We're none of us getting any younger. In fact, more of us are getting older. A glance at British demographics shows that half the population is now over 40, while 44 per cent fall into the over 50s age group. So, it should, I suppose, be cause for celebration that Twiggy, 55, is clambering back on to the catwalk to front Age Concern's campaign to combat "ageism" in advertising.

We're none of us getting any younger. In fact, more of us are getting older. A glance at British demographics shows that half the population is now over 40, while 44 per cent fall into the over 50s age group. So, it should, I suppose, be cause for celebration that Twiggy, 55, is clambering back on to the catwalk to front Age Concern's campaign to combat "ageism" in advertising.

Following a survey conducted by Age Concern, which showed that 74 per cent of people over 50 feel that advertising portrays them negatively while 74 per cent "cannot relate" to current ads, the charity is backing a drive to promote better awareness of this group.

"Older consumers want to see attractive older men and women advertising products aimed at them," says a spokesperson for the charity. Thus, Twiggy, the face that launched a thousand eating disorders back in the Sixties, has been relaunched as the (tautly) concerned face of older women who feel they're discriminated against by a beauty industry which insists on advertising anti-ageing creams with pictures of girls barely out of their teens.

"It is vital," says the newly politicised model-turned-actress, "that older people are treated equally as consumers of beauty products."

As emancipation campaigns go, it's not exactly up there with Emmeline Pankhurst and Rosa Luxemburg, but you can see what she means. Sort of.

Personally, I have never woken up in the morning crushed by the knowledge that I am inadequately advertised to. Indeed I am less irritated by images of flawless teenagers than I am by the smug harpy advertising RoC wrinkle cream who flashes her can-you-believe-it? smile at the camera and announces "I'm 44!". This may be because I am 43, and not in nearly as good nick, but there is a wider principle at stake.

On the heels of the Age Concern campaign, the picture files of almost every national newspaper have been raided for positive images of older women. Joan Collins (102? 103? Who knows Joanie's real age?), her face a rigid testimony to the mortician's art, is invariably wheeled out, as are the extensively nipped and tucked Anne Robinson, 60, and Sharon Osbourne, 52.

Now, to paraphrase Mrs Merton, what can be the beauty secret shared by these multi-millionairesses? I'm thrilled to learn that Mrs Osbourne's £120,000 face-and-body lift was a matter of "self-esteem and empowerment", but I'm not sure how it's supposed to make the rest of us, who are guilty spending more than £20 on a jar of face cream, feel better about ourselves.

Still, there's no arguing with an acronym: Marks & Spencer, keen to plug the marketing gap between thongs and winceyette bloomers, has come up with Disco (Discerning, of Increasing Years, Stylish and Comfortably Off) woman. I'm wondering if there's another niche in the marketing structure, for unreconstructed Dogs (Discerning, Of increasing years, Grinding their teeth in exasperation) - women who are fed up with being told there's nothing wrong with being old, as long as you don't look it.

It is true that there is an expanding market of affluent baby boomers in the Western world, possibly the first generation of over-50s who are more inclined to spend than to save. Age Concern, naturally, looks to the rights of these consumers - the charity wants to see unfair "age barriers" lifted in respect of loans, car hire, travel insurance etc - and I suspect that, as the demographic reality begins to bite, businesses will give older customers the respect their finances deserve.

But the elderly are a widely disparate economic group; while advertisers seek ever more sensitive ways to relieve affluent over-50s of their money, the less affluent elderly are living in conditions that are the shame of Europe.

Two million - one in five - British pensioners are currently living in poverty.

Public provision of care homes has all but disappeared and a whole new consumer group with little in the way of choice, much less respect, has been created as old people are forced to pay their life savings for frequently inadequate private care. It's horrible to think how quickly the "active consumer" cited in "grey power" rhetoric becomes tragically passive - another figure on another balance sheet.

It's even more horrible to consider an estimated 7-10 per cent of old people in Britain are subject to abuse - that's not being offended by inappropriate advertising, but actual physical, emotional and financial abuse. I've always admired Maurice Chevalier's stylish assertion that "old age is better than the alternative". Unfortunately, for many British pensioners, that may no longer be true.

Respect for the elderly needs to go further than applause for celebrity facelifts. The 55-year-old Twiggy (who, for the record, has yet to go under the knife) is lovely, but she's no more representative of her generation now than she was at 16 and her "positive image" campaign seems to me indicative of a culture obsessed by cosmetics.

Image is important. But - the older we get, the more most people realise - it isn't everything.