The fuss began last month after an episode of the BBC2 documentary series Horizon investigated the £25 billion anti-ageing product industry, and some of the crazy claims it makes. The surprise conclusion was that yes, in fact, there was one across-the-counter product that could help make wrinkles disappear. And that product - amazingly - cost just £16.75 for a 30ml jar and could be bought at your local branch of Boots. The programme aired on the night of 27 March 2007. Within just 24 hours, sales of No7 Protect and Preserve serum had increased by 2,000 per cent, the store's online catalogue had been hit by over 4,000 requests, women from America were calling to find out how they could get some too and single jars were being sold on eBay for up to £100. As of a month ago, when I first started researching this story, there was nowhere, apparently, that British women weren't hitting each other over the head to get a pot of it.

However, increasingly women are settling only for the harder stuff: according to Liz Walker, proprietor of the House of Beauty in Barnsley, Yorkshire, it's not wrinkle serum her predominantly working-class clientele are clamouring for now, it's Botox. 'Supermarket workers, school dinner ladies, they're all saving up for it,' she says. 'And there are no-holds-barred as to how far they'll go for all the other stuff either. We're now using machines they don't even use in London in order to get more immediate results. Well, a pampering facial or a nice cream is all very well, but it's not going to make those wrinkles completely disappear, is it?'

Well hooray. It's official. I'm not the only age-orexic around. I'm not alone in thinking the idea of being 50 is an absolute outrage. I'm not alone in believing middle age happens only if you are ornery or slovenly enough to let it. Here is clear-cut, concrete proof that, up and down the country, it's all pretty much the same. We are now, amazingly, more obsessed about being young than we are about being size zero. And I speak with authority, having spent most of London Fashion Week backstage for the next issue of Vogue. (Yes, models still need to be thin, but only because it makes them look more adolescent.) In other words, if you want to insult the average British woman, don't guess her weight, just guess her age. Perhaps insult is not quite the right word. Indeed, if you were to look at the photograph on the previous page and tell me you see an attractive middle-aged woman (for that technically is what I am at 46) I'd not be merely insulted, I'd feel, on some level, that I had failed.

As I write this, I am pinching the skin just below the waistband of my miniskirt. It is not fat, it is surplus skin, a badge, you might say, of the two overwhelmingly wonderful children I have produced. It is soft. It is maternal. It is appropriate. Except, of course, I don't see it that way. I see it is as a telltale sign of me being three years shy of my 50th birthday. That layer of skin is what stands between me and the pre-baby body I had in my early 30s and which I feel is my responsibility, as a fully paid-up member of the glossy-magazine industry, still to have.

To that end I've booked a course of something called Titan, a laser-like device (endorsed by Mr and Mrs Tom Cruise according to a recent issue of heat) to tighten skin by blasting infra-red rays into the tissue and shrink it (as my Pimlico 'derm', Dr Elizabeth Dancey puts it) 'like a woollen sweater in the dryer'. I reckon this, plus no carbs and lots of Bikram yoga, should nail it in time for wearing a bikini. The wrinkles, the sunkenness round the cheekbones, that's more of a problem. As a recent study of the passport photo I had taken just after my last baby was born rather devastatingly revealed, I cannot kid myself any more into thinking my face is the same face I had four years ago. As I was told when I went on something called a Visia Complexion Analysis machine at Beyond Spa in London's Harvey Nichols, all those years of frying in Bergasol with bits of tinfoil up my nostrils mean there's no serum in the world that is going to make any difference at this point.

A whopping 70 per cent of British women in my age bracket have skin younger than mine. What I can and will have, though, is some medical microdermabrasion and a course of something called IPL, a laser treatment that feels like a rubber band being twanged all over your face and burns into your cellular tissue to create new collagen. If it weren't for the fact that the one time I had Botox it made me look older rather than younger, I'd have some of that too.

A significant part of me knows there is something very wrong and rather primitive going on here. That it is not right for a perfectly evolved, university-educated, maths-literate woman in her forties to compete, on the tummy front, with her 17-year-old stepson's girlfriend, to feel patronised rather than flattered when a talent scout from the Dove Campaign for Real Beauty asked if I'd like to audition for the latest ad (as someone did in the glove department of Liberty last year). Who do I think I am, after all? Liz Hurley? And what is the point when I've had my babies and met the man I want to spend the rest of my life with?

Like the writer Helena Frith Powell, 39, who has gone one step further than me by having lipo on her middle, this chasing business makes me feel slightly 'superficial and deranged'. It makes me feel sort of wimpy too. After all, us oldies are, technically speaking, in the majority, and we have the power, economically and numbers-wise, not to feel bulldozed. According to the Office for National Statistics, nearly half the population is over 50 and, by 2031, nearly a quarter of the population will be over retirement age. Besides who wants to be one of those saddos, as director and novelist Nora Ephron recently described them, 'who make the mistake of thinking that because they look good for however old they are, they look empirically good ... [resulting in] way too many tank tops on women who are 50 and 60'. Me? A pathetic fiftysomething in a tank top? No way!

And yet. The idea of me dressing or behaving any differently to the way I do now in the short space of three years, of waking up one sunny morning and deciding to throw away all those micro miniskirts and bikinis is so out there, so absurd, as perhaps not even to happen. Joan Collins has worked her look well into her seventies. Why can't I do that with mine?

Deluded? Undoubtedly. How can I possibly kid myself into thinking the age process is negotiable, and why on earth am I participating in a battle that I know I cannot win? At the same time if I keep eating those cruciferous vegetables and keep seeing Dr Dancey and have enough of those hugely expensive Bupa medicals, who knows what I am going to look like in 20 years' time? We've come a long way baby in the last couple of decades, and when I see pictures of my mother in the early 1990s, when she was 46, looking perfectly attractive in a grown-up calf-length suit and hose, and sporting the odd grey hair, I cannot for the life of me believe that is the age I am now. Is that what nudging 50 was supposed to look like then? Because it sure as eggs isn't what it's supposed to look like now.

Since time immemorial we women have been at it, slapping on the arsenic face masks and so forth to make ourselves look more of a child-bearing age for our menfolk, to compete on the looks front with other women. As the philosopher and critic John Berger once said, men 'act' and women 'appear' and, until men can have babies, that's probably the way it will always be.

The difference between now and 15, perhaps even 10 years ago, when mummies were just about allowed to look like mummies, politicians were just about allowed to look middle-aged, and the cult of youth hadn't quite got such a vice-like grip on our lives, is that at least we knew then what not to aspire to. At least we felt we had an element of choice. In this topsy-turvy, one-age-fits-all culture of ours, where daughters, mothers and grandmothers shop at Topshop, where 50 isn't so much the new 40, so much as 70 is the new 30 (ie Sophia Loren posing nude in the Pirelli calendar); where one cannot seem to pick up a newspaper or magazine without reading about some granny who has just been vaginally rejuvenated, and where, furthermore, every aspect of life, including politics, is beginning to feel more and more virtual, the decision of a fortyplusser to dress like Peaches Geldof isn't so much a decision she makes as a cultural imperative that has been imposed on her. Be the schlumpy granny at the school gates whom none of the other dads fancy by all means, but only if you don't mind being perceived as something of a freak, or at a socioeconomic disadvantage.

As a recent ground-breaking UK study of 750 sets of female twins proved, working-class women age seven years faster than women further up the social ladder. In other words, if you want to paint a portrait of blue-collar Britain, make it obese and give it plenty of wrinkles.

Alex Kuczynski, the New York Times writer and author of Beauty Junkies, a sobering account of the cosmetic-surgery industry, puts it like this: 'What woman doesn't look at an issue of National Geographic, sees the picture of the 70-year-old Afghan woman with lines etched into her face, reads the caption and sees she's actually only 36, and thinks, "Well, aren't I lucky I don't live in the developing world?"

'Looking young isn't saying, "I've got good genes", so much as saying, "I can afford the monthly derm visits, I can afford the creams, I can afford the trainer". Just like being super-slim is an indication that you can afford to eat right and live well, so is looking young for your age. It's the equivalent of having an expensive handbag.'

'It's true the cult of youth is very much part of the vernacular,' agrees Susie Orbach, formidable author of Fat is a Feminist Issue and adviser to the Dove Campaign for Real Beauty. 'In a way it is just a different version of the whole body-image dilemma, the way we are all so complicit in what amounts to a form of bound feet. But women are not passive idiots. Visual culture, PR, marketing, are all-powerful in today's society. And it is only representing beautiful women of different ages through visual culture and marketing, letting it penetrate people's eyes, that mindsets are going to change. That is precisely what the Dove campaign is trying to do, to say that actually 50 is not the new 30 - it is 50, and gorgeous. Ideology, people thinking that they're messed up by feeling this way but are powerless to do anything about it, that's not going to do a thing.'

Could it be that life for a woman approaching the menopause years is better elsewhere? Very possibly, yes. Take Japan for example, where the tradition of wabi-sabi, which reveres the imperfections of age, wind and weather, still reigns. Take France too, where women really do, like wine, seem to get better with age - look at Ségolène Royal. In this nation of ours where, as in America, female newscasters have to look positively foetal to keep their jobs, where there are so very many products out there on the market (wrinkle cream being the mere tip of the iceberg) that trade on our fear of age, where insecurity is fostered even in the most secure among us, it's a teensy bit different.

'I have a track record, I am a mother of two, I will be 40 in 18 months,' offers Kirsty Young, Channel Five newsreader and presenter of Desert Island Discs. 'The men I want to appeal to - and that is to say my husband principally - are not fans of the Paris Hilton school of beauty, which makes me feel pretty secure. But I am in a business where looks are valued equally with the ability to do the job. So I am torn and probably just a little bit hypocritical and if, midway through my fifties, my eyes got very baggy then yes, I will possibly/maybe/not sure if I could when it comes to the crunch have surgery. Diane Sawyer [anchorwoman for ABC's Good Morning America] is a woman I admire and who looks quite superb in my view, but I cannot imagine that is all down to two litres of water a day and regular Bikram.'

Documentarist Molly Dineen, 48, has always prided herself on not caring about her age. 'I've been in this timeless, one-of-the-blokes thing, since my twenties, gambolling around in flat shoes and a kilt, with a scrubbed face, that's always been my look.

'Part of that is because I've always felt that if I don't make an effort on the heels and make-up front then I can't be judged. Part of it is denial, too. Every mirror in our house seems to be backlit, so no wonder I skip out every morning thinking, "But I'm absolutely gorgeous! How do I get away with it? All that abuse and not one effing wrinkle!".'

To promote her latest documentary however, The Lie of the Land, she found herself having to pose for all sorts of photographs for the press. It was the one she saw of herself in Country Life that made her change everything she'd thought about her looks thus far. 'I couldn't believe it. There was this incredibly old woman from the Saga holiday brochure. It wasn't that I looked nearly 50, I looked nearly 70. Perhaps it is to do with being tired, but it was a real turning point for me, a point when I realised I had to do something about it.'

What? Meaning my friend Molly, whom I have never seen wearing one scrap of make-up, who claims to feel like Dick Emery in heels, is actually ready to go under the needle?

'Oh, right now? Like a shot. All my life I've lived slightly for tomorrow. Tomorrow I'm going to wear this. Tomorrow I'm going to be a pop star. Tomorrow I'll sort my life out. I suppose what this picture made me realise is tomorrow is actually today, and something must be done. It's like that thing of being on a plane and they're handing out some questionnaire and you're a bit bored so you decided you'll fill in the boxes and realising you are in the bracket that says 45-60. You think no, they're joking. But they're not. You are.'

'It's true that most of us live in a state of denial,' says writer Lionel Shriver, who will be turning 50 this month. 'And we're encouraged to feel that way because that's supposed to be putting up the good fight. In one way I feel envious of the women who can hang it up, who don't have to go for the nine-mile run at nine o'clock every night, who can have dessert, or sit down to an entire tin of shortbread because they feel like it. The truth of the matter is that we will never be able to decide when we don't care any more, because women will always be judged on their appearance, by men and by other women. For example, I was watching Newsnight Review last night and I didn't give one single thought to what the two men on the couch looked like. But the woman? She was wearing this weird red frilly jumper with this turtleneck underneath. I kept slapping my wrist, thinking, "Stop it, how could you?" But it kept going through my mind, over and over again: she really shouldn't have worn that.'

Shriver is preternaturally young-looking for her age (and recently wrote an article on the subject for Vogue), but wonders how much longer that will last. 'Most of the time I'm not aware of how I trade on my looks, but it's going to hit me hard when I can't do it any more. I still do it, but I know I'm living on borrowed time.'

Alex Kuczynski, meanwhile, has sworn off a habit of collagen and Restylane injections after researching her book. She is acutely aware of the fact that, as she puts it in the last chapter, 'the process of constant scrutiny and constant evaluation and constant tuning and touching up ... often feels like winning a series of small battles but losing the war'. At the same time she, like me, has a hard time coming to terms with the idea of being an older woman, of others perceiving her as such. 'When a photographer photographed me recently for a magazine and asked me if I wanted him to put me up for the latest LL Bean catalogue, I wanted to kill myself!'

How dare we, right? How could we be so unhelpful to the cause, so disloyal to the generation of women before us who fought so hard in order for us not to feel like we had to define ourselves by our looks, our age and our sexuality. And why on earth, given the fact that we are in the majority, aren't we jamming open our windows and shouting out that we're mad as hell and we're not going to take it any more? Why are we helping to make ourselves invisible, tacitly agreeing not to be represented in the media, in the workplace. Why are we colluding in making the playing field even less level than it was before?

'Oh, the inequality between men and women is much greater now than when I was at university in the Sixties,' says newsreader Anna Ford, 63. 'And I accuse the BBC of ageism on a grand scale. I mean if you look at society there are millions upon millions of women over the age of 60 and they are not reflected on our TV screens in any way. We are forcing ourselves into straitjackets that in the past have been created by masculine society. Luckily there are some of us out there who are beginning to say no, they're not going to do that any longer, but that decision may come over a certain age ...'

Perhaps it really is a matter of time. Perhaps once one actually does reach the big five-0 and/or gets those hot flushes one can, as it were, relax, let go and not only order the dessert but eat it too.

'Except it's not letting go,' insists Anna Ford, who last year decided not to renew her contract with the BBC, and at the same time to stop dyeing her hair. 'It's more that I don't want to pretend any longer that I am younger than I am. I don't want to be judged by what jacket I am wearing or whether I look good or bad for my age. Going white like my mother did when she was 39 saves money and means I can be me!

'Did I think this way at your age? No, of course I didn't, it happened over a period of time and it happened because I wanted it to happen. But, at the same time, one of things I set myself a long time ago was to try and get the inside and the outside to match. Feeling cowed and afraid inside and looking calm and dressed beautifully and wearing the right nail varnish - which was what I did when I was younger - is not, as I have learnt, the key to happiness, it is the treadmill of failure. The step I have made in the last year has been incredibly positive. It's a lovely change.'

Having the inside match the outside. Now there's a thing. Perhaps part of the reason why women are getting sadder and sadder about the ageing process, why everyone's so nuts in, say, Hollywood, is because their outer carapaces, their spookily unfurrowed brows, their mask-like faces, in no way match what they are feeling inside. What does being the Playboy centrefold while being prescribed HRT, comparing oneself to women 30 years our junior, constantly denying our mortality, do to the human psyche, after all?

In many ways I long to be off the radar of the 'male gaze', to achieve all those things I can achieve when my self-esteem isn't so tightly bound up with my sexuality, my looks and my age, to live that truthful, authentic, somewhat spiritual existence which is predicated on none of the above; to become, as I once heard someone say, the person 'your dog thinks you are'.

I look at one of my personal role models, Alex Shulman, 49, editor of British Vogue, who has made a conscious decision not to fight a battle she cannot ultimately win, who claims she is always fighting the urge to 'let my hair go grey and wear smocks and thick glasses'. I listen to her very carefully when she offers the opinion that feeling weird about getting older is very tightly bound up with feeling weird about what one has not achieved in one's life thus far, and cleverly argues 'that, if one is so very competitive, wouldn't it make sense to opt out of the competition that can never be won? Isn't being in a place where you can never win rather depressing?'

I look, too, at my mother, a dedicated human-rights activist, who decided that defining oneself by one's outward appearance was on the road to going nowhere when she was just a little bit older than me. Here is someone who, at 63, has very much got her priorities in order, wouldn't dream of depriving herself of the most fattening pudding on the menu if she so felt like it and, although constantly complaining about her weight, feels happier and more fulfilled, more authentic, than she has ever felt in her life. And it shows.

The desire to relive my youth with the financial and, to a certain extent, emotional security I found as an adult, feeling resentful that I didn't have as good a time in my tortured twenties as the twentysomethings I see around me now appear to be having ... that's never going to go away. But, at the same time, I can feel a smidgen of a shift in my way of thinking, a glimmer that actually, middle age, if I let it, could be more fabulous than I think. Picture it. A year-round mahogany tan, waist-length silver-grey hair and rouge-noir lipstick. What do you think?