My parents' generation, at my age, all had false teeth. My generation fondly expects to go to the grave with a full set of snappers. The extension of the life of our teeth through developing dental technology, clearly, has happened, but the biogerontologist Aubrey de Grey believes science will take us much further. With careful maintenance, he argues, there is no reason the human body shouldn't last for ever. Or at least for a millennium or so. The central goal of De Grey's work in Cambridge University's department of genetics and as chairman of the Methuselah Foundation is, he writes on his website, "to expedite the development of a true cure for human ageing". He is waging, as he likes to say, "a war on age".

Before you get too excited, he doesn't yet know what tactics will win this war. But he has a broad strategy. "My approach is to start from the straightforward principle that our body is a machine," he says. "A very complicated machine, but none the less a machine, and it can be subjected to maintenance and repair in the same way as a simple machine, like a car. We all know that with adequate care it's possible to keep a car on the road indefinitely. Those vehicles, for example, that take part in the London-to-Brighton run were not meant to last 100 years. And it's the same with the human body. The only problem is that the body is much more complicated than any machine that we have. And, on top of that, we didn't design the human body, and therefore we have to discover how it works in order to figure out how to make it work better and carry on working."

De Grey believes that medical treatments - "stem cell treatments, gene therapies, things like that. Certainly nothing that would be cannibalistic" - will be the means of extending life. And as those treatments evolve, so people who are now 30 or so will be able to reach a "life extension escape velocity" which will enable them to elude the gravity of our current lifespan.

All it will take, he says, is three decades of technological development: "The idea is that 30 years on from the initial point the therapies will be so significantly improved that they can be used ever more comprehensively on the same people, bringing better and better results. The initial therapies will repair and obviate the things that are easiest." Subject to funding, he reckons, there is a 50% chance of achieving life extension escape velocity within 30 years. Eventually, he predicted last year, someone who might have lived to 110 without intervention will be able to chalk up 1,000 years.

The therapies he talks about will not be targeting the things that go wrong at the end of life - the degenerative diseases and loss of motor function - but their precursors, the changes that occur throughout life but which are manifested most devastatingly in old age. Heart disease, for example, "happens, mainly, because of the accumulation of fatty deposits in the artery wall. That accumulation has to proceed, gradually, to a certain critical degree, before it's bad for us. But if you look at the arteries of even a kid, you find the precursors of that process. So what I focus on is these intermediates: things that are happening throughout life, from the beginning, accumulating gradually as a side-effect of metabolism. Initially, they're inert, but when they reach a certain level of abundance, they screw up the metabolism, they stop the body from working well."

By targeting the diseases of old age before decrepitude creeps in, De Grey believes he can avoid the common accusation against theorists of longevity: that they will only prolong frailty. "We are talking about extending 'healthy' life," he says. "We're not extending the bad part of life. And the extension of the healthy part of life is not limited by what we currently have as total lifespan. The aim is to postpone frailty, postpone degenerative disease, debilitation and so on and thereby shorten the period at the end of life, which is passed in a decrepit or disabled state, while extending life as a whole."

Naturally, there are countless objections to the idea of prolonging life. De Grey has an answer for them all. What if the extension of life leads to overpopulation, for example? Well, he has responded in the past, what if the French prime minister had banned Pasteur from promoting hygiene on the same grounds? Moreover, he says, we have no right to bar future generations from something that will benefit them. On his website, he writes: "Pretending that we will be so unable to cope with future problems that it's better to condemn indefinite millions to the puny lifespan of their ancestors is a sick joke anyway, but even sicker when we consider how implausible it is that such problems would be any worse or harder to tackle than those we've tackled in the past ... For example, who would have thought in 1850 that society would submit to the indignity of wearing absurd rubber contraptions every time they had sex, just to arrest the population explosion that followed the near-elimination of infant mortality?"

As for the "pensions time bomb", De Grey argues that since he is talking of extending active life, not frailty, people will be able to continue working far longer - in fact, they will be able to retire for a while, then enter a new career. Society is burdened by the frail, he says. In his brave new world, there will be no frailty, and so no burden.

To the onlooker, the commercial attractions of the elixir of youth would seem to be overwhelming. Why hasn't there been massive interest from the big pharmaceutical companies? As much interest, say, as in baldness or erectile dysfunction therapies?

"The answer is mainly psychological. We've spent the last few millennia aware that senescence is horrible but knowing nevertheless that it's inevitable. We've had to find some mechanism to put it out of our minds so we can get on with our miserably short lives. There's nothing wrong with making the best of one's declining years, but what does annoy me is the fatalism. Now that we're seriously in range of finding therapies that actually work against ageing, this apathy, of course, becomes an enormous part of the problem."

· For more about De Grey's work, visit www.sens.org