Wendy Savage, champion of women's rights in childbirth, is still champing at the bit. Sitting on a sofa in her Islington house, she is a figure of barely contained energy. Slender, steely haired, barefoot, she gets up from time to time to find a book or a pamphlet she can press into my hands to complete her case. She does not look you in the eye much, preferring to gaze into the middle distance, following the train of thought that is pulling her along.

An unstoppable train it is too. With the publication of a new book, Caesarean Birth in Britain (co-authored by Helen Churchill and Colin Francome) she has re-entered the debate on the most controversial aspect of childbirth today - why the caesarean rate is rising inexorably, from 12% in 1990 to 23%, almost one in four births, today.

The book puts up various possible explanations, based on the research literature and a new survey of the opinions of 100 consultant obstetricians. These range from the rising fear of litigation, quoted by more than half of consultants, to current working practices, since high rates of caesareans are more likely when there aren't enough staff. Then, of course, there is the fraught question of patient choice; of whether women are "too posh to push".

I am surprised that Savage homes in on this when I ask her to explain what is causing the rise. "One of the problems," she says, "is that obstetricians don't find it easy to say no when a woman says she wants a caesarean." It's odd to hear the great defender of woman-centred medicine saying doctors should say no to women. "I don't think most women are actually coming in and just saying, 'I want a caesarean', but if they've had a badly managed first birth ending in a caesarean, a lot of women want an elective caesarean the next time. I would say to them, 'It won't be the same the second time around', and in my experience those women can go on to have a vaginal birth."

But the book also says it is important to focus on "the doctors' role in influencing women's choice" towards caesarean - so who is really doing the choosing, the patient or the doctor? "It's subtle," Savage says. "I think doctors feel that it's not so much the fear of litigation, but it's more that women and their families expect everything to be perfect, and if it is not they are upset, and doctors are influenced by that. I think women and their families have to understand that life is uncertain."

Now 71, Savage has been arguing against what she sees as the unnecessary use of caesareans for many years. In 1985 she became a cause celebre when she was suspended from her job at the London Hospital (where she was the only woman consultant obstetrician) over accusations of incompetence, centring on births in which she was said to have delayed performing caesareans. Shocked and furious, Savage was also heartened by the numbers of GPs and healthcare workers who supported her. The suspension was seen as politically motivated, stemming from colleagues' hostility to her enthusiasm for community healthcare and home births rather than hi-tech hospital-based medicine. She was cleared of any suspicion of incompetence, and wrote a polemical book, A Savage Enquiry, which argued that "I and many of my supporters saw my suspension as part of the continuing struggle about who controls childbirth."

At the time, she felt the scandal and the debate put the issue of unnecessary reliance on caesarean section on the map, and many things followed that heartened her - from the Changing Childbirth government policy adopted in 1993, which advocated woman-centred care, to the Nice guidelines in 2004 that recommended bringing down caesarean rates. But regardless, the rate of caesareans continues to rise. Caesarean Birth in Britain is an update of the 1993 title of the same name, but then the caesarean rate was a lot lower, at 13%.

As well as being a proponent of natural childbirth, Savage has been a convinced campaigner in favour of abortion. She finds the current state of the debate dismaying. "I'm very disappointed in Stuart Campbell [the obstetrician who has pioneered new imaging of foetuses] putting this emphasis on ultrasound pictures. Women know that their foetus is becoming a baby. They don't need to be shown that. It's patronising."

When I ask her what first brought her into defending women's rights to abortion, she talks about going to practise medicine in Nigeria in the 1960s. "I saw young women dying. One day my housemate came and said she was pregnant - she was 17. I told her to go and tell her parents." Savage pauses, looks at the floor. Her hands are shaking and her cheeks are wet. Forty years on, she is reliving the moment of horror. "She went to see a native doctor and came back and I could see she was ill so I took her to the hospital. Half an hour later she was dead. She was such a beautiful, happy young woman, Anastasia her name was. That's when I realised that women will do anything to get rid of a pregnancy they don't want. I realised then - you have to listen to the women."

Savage has always displayed heroic energy on a personal as well as political level. She was one of the pioneers who showed that women could combine a high-level career in medicine with parenthood, since she had four children while pursuing her medical work. She has been a living embodiment of her ideals, since all four births were straightforward vaginal deliveries. With the fourth birth, she went into labour during a wardround and was back at work three weeks later. "My one regret," she says, "is that I never had a home birth."

As I talk to her I find myself admiring her on so many grounds: her drive, her energy, her desire to champion what she feels is best for women. But I am made uneasy by how her work plays in the current environment. Her emphasis is on making individual women feel that vaginal birth is preferable to caesarean birth to the extent that they should never, ever have an "unnecessary" caesarean - one without an absolutely compelling medical reason. While some obstetricians say a planned caesarean without medical indication is no riskier than vaginal birth, she puts the opposite view: "You are more likely to die," she says, but admits, "It's not a huge difference." (Statistics on maternal mortality do not distinguish between planned caesarean for medical reasons and planned caesarean because of maternal request, and this is why they remain a grey area.) She puts a great deal of emphasis on the trauma and long recovery time of a caesarean.

But this emphasis on trying to bring down the caesarean rate would be fine if vaginal births were being well-managed, with decent one-to-one support in a respectful environment. But labour wards are often unsupportive, chaotic environments, where a woman attempting vaginal delivery has to endure continuous monitoring, endless examinations, vast numbers of midwives, students, and doctors, poor communication and conflicting advice. Often, she has a protracted and unhappy birth, maybe ending with ventouse or forceps or an emergency caesarean. In comparison, an elective caesarean even without a compelling medical reason can feel like a rational choice. I try to put this to Savage, but I feel a chill descend as soon as I do so.

"Say you were still practising and I came to you telling you that with my first birth I had found it so miserable being in so much pain, being seen by so many indifferent staff, strapped up to so many machines, that I wanted an elective caesarean next time, what would you say?" "I would say, have a home birth," says Savage, looking steelier than ever. "Since your second labour is likely to be much shorter and easier than your first birth. You are rich enough to have an independent midwife at home."

I wonder how many women who have had a difficult first birth would feel easy choosing a home birth second time, and I wonder if Savage understands how hard it is for women who haven't had her kind of childbirth experience to say they found natural birth traumatic rather than empowering. Next to Savage's certainty I feel as if I have let down the side by not taking the correct line: vaginal birth good, caesarean bad.

"Don't you think we should focus more on putting the system right than making women feel guilty?" I say, and here we find common ground. "What we have to do," she says, "is make the experience better for women. Is the problem partly the way we set up our delivery wards - they are noisy, full of bright, fluorescent light, with people walking in and out talking? That all goes against the quiet and calm a woman needs. And women want continuity of care. If midwives were organised in little groups in the community to give continuity of care to women, that would be better. But there is a lot of hostility to that from managers."

The tragic reality is that in some ways women in childbirth now face a worse situation than they did when Savage first qualified. "Some things have got better. But skills and expertise have been lost. When I was training a medical student had to do at least 20 deliveries, which meant staying right through the labour, not just coming in at the end. Now that would be seen as a waste of a medical student's time. Also, when I started out you worked much longer hours - so as a woman in labour you were much more likely to see the same doctor or midwife. I could start with a woman at 8pm and go on till the next morning. That was terribly important."

It is depressing to hear this veteran campaigner look back over more than 40 years and conclude: "I think the system is less woman-centred now".

· Caesarean Birth in Britain is published by Middlesex University Press (ISBN: 1 904750 17 6). It is priced at £18. To purchase a copy please visit www.mupress.co.uk