For four weeks last month I sat in the front row of catwalk shows in London, Milan, Paris and New York watching painfully thin models walking up and down inches from my nose.

Kate Moss, the original 'superwaif', was looking positively curvaceous compared to the current bunch of underweight teenagers.

For those used to the fashion industry there was nothing unusual about the shows at all. But for me it was the end, it was then that I decided to resign as editor of Marie Claire magazine.

I had reached the point where I had simply had enough of working in an industry that pretends to support women while it bombards them with impossible images of perfection day after day, undermining their self-confidence, their health and hard-earned cash.

My decision to quit was partly precipitated by the failure of a campaign I started a year ago to encourage magazines, designers and advertisers to use models with more realistic, representative body images. Then I could not have anticipated the extraordinarily hostile reaction to my fairly innocuous suggestions from fellow editors and designers. A year later I have come to realise the sheer terrorism of the fashion industry and accept that, alone, I cannot change things.

But in spring last year I was full of optimism that we could change. I believed wholeheartedly that we could stop magazines and advertisers using underweight girls as fashion icons. I had already banned diets and slimming advice from our pages but after meeting Gisele, the Brazilian supermodel credited with bringing 'curves to the catwalk', and discovering that she is a tiny size 8, I decided to challenge the status quo.

We decided to publish two covers for the same edition - one featuring Sophie Dahl, a size 12; the other, Pamela Anderson, a minute size 6 - and we asked readers to chose between the skinny, cosmetically enhanced 'perfection', or a more attainable, but still very beautiful curvy woman. Sophie Dahl won by an overwhelming majority.

But you would think that we had declared war. The reaction was staggering. Newspapers, radio and TV stations were largely behind us. They welcomed the opportunity to demystify the closed and cliquey world of fashion. Our covers were in the national press for weeks - even making headlines in the New York Post. I had requests from universities here and abroad wanting to include our experiment in their college courses. Documentaries were made in the US and Germany. The response from readers was unprecedented. We received 4,000 letters in two weeks.

However, the very people from whom I had expected the most support - my fellow female editors - were unanimous in their disapproval.

I was invited to speak at the Body Image Summit set up by Tessa Jowell, Minister for Women in June 2000 to debate the influence of media images on rising problems of anorexia and bulimia among women. One suggestion was that a group - consisting of editors, designers, young women readers and professionals who treat women with eating disorders - should get together on a regular basis to monitor the industry, bring in guidelines on using girls under a certain body size and weight and discuss ways the industry could evolve. My job was to gather these people: not one single other editor agreed to take part.

Instead most of them were hostile and aggressive. Jo Elvin, then editor of New Woman, accused Marie Claire of 'discriminating against thin women'. (As if there aren't enough role models in the media for thinness, from Jennifer Aniston to Gwyneth Paltrow to American supermodel Maggie Rizer.) Another fashion editor made the point that there had always been skinny women - look at Twiggy, for example. Jasper Conran absurdly suggested we should be looking at obesity as a serious health problem instead of anorexia and bulimia. I didn't bother to point out that people with obesity were not usually put on magazine covers as fashion icons.

The next day, after the summit, I received a fax, signed by nearly all the other editors of women¿s magazines and some model agencies, stating that they would not be following any initiative to expand the types of women featured in their magazines - one of the topics up for discussion at the summit was how to introduce more black and asian women onto the pages of Britain's glossies.

When I read the list of names, I felt like giving up the fight there and then. I was isolated, sickened to my stomach that something so positive had been turned into a petty catfight by women I respected and admired. They were my peers, friends, and colleagues I sat next to in the front row of the fashion shows. They were also the most important, influential group of women in the business, the only people who could change the fashion and beauty industry. Why were they so reluctant to even think about change?

Like me, they had sat at the summit while a group of teenage girls, black, Asian and white, some fat, some thin, had berated us all for what we were doing to their lives. I had found it moving to listen to these young women, brave enough to come and talk in front of all these scary high profile people. Anyway, to me, it made good business sense to listen to them and address their concerns: why alienate your readers? I could see those teenagers turning away from magazines because we seemed hopelessly outmoded, old fashioned, unattainable. But I was clearly alone.

The other editors seemed to revel in the chance to counter attack. Alexandra Shulman, editor of Vogue, denounced the whole campaign as a promotional tool for Marie Claire and said that suggestions of an agreement to set up a self-regulatory body within the industry was 'totally out of order'. Debbie Bee, then editor of Nova - a supposedly cutting edge fashion magazine for young women - asserted in her editorial the following month that magazines didn't cause anorexia as readers were intelligent enough to differentiate between an idealised model and real life.

Fiona McIntosh, editor of Elle, published a cover picture of Calista Flockhart with the caption, 'I'm thin, so what?' She accused me of 'betraying the editors' code'. Frankly, I didn't even know there was a code; only one, surely, to put your readers first.

Some model agencies blacklisted the magazine. Storm, who represent Sophie Dahl and who you would have thought would have been happy that one of their models was being held up as an example of healthy gorgeousness, told us that we could no longer book any of their girls. Several publicists from Hollywood, reacting both to the cover and a feature called 'Lollipop ladies' about women in Hollywood whose heads are too big for their tiny bodies, wrote to me saying their stars would not be gracing our covers - ever.

I had clearly put my head too far above the parapet. I realised that far from being the influential, trend-setters I had thought magazine editors are more often ruled by fear - and advertisers. No-one feels that they can afford to be different. They are happy to settle, instead for free handbags, and relentless glamour.

To be honest, it would have been very easy to give up then. Every time the contacts of a fashion shoot landed on my desk with a model whose ribs showed, whose bony shoulders and collar bone could have cut glass, whose legs were like sticks, we could have published them anyway and said, 'oh well, we tried'. But we didn't. We threw them out, set up a reshoot, and eventually, slowly, agencies started to take us seriously and would only send girls with curves in all the right places.

I cannot deny the campaign got the magazine talked and written about. The choice of covers got the readers involved and made them have a little bit of power for a change; they got to choose who they wanted on the cover. The Sophie Dahl cover started to sell out, and readers would phone me, frantic, saying, 'I could only buy the Pamela Anderson cover, but I want you to register my vote for Sophie.' It could never have been a scientific exercise - subscribers to the magazine had to take pot luck; but still they would phone up saying, 'No, I wanted Sophie!'

But I was dismayed by accusations that this was just another way to boost sales. I suffered from anorexia from the age of 11 until my late twenties and understand first hand the damaging effect of a daily diet of unrealistically tiny role models gracing the pages of the magazines that I was addicted to. Although it did not cause my illness, the images definitely perpetuated the hatred I had for my own body.

I agree with Debbie Bee of Nova that young women are intelligent enough to be able to tell the difference between a model and real life but the effects are often subliminal. One piece of research we did at Marie Claire was to ask a group of intelligent professional women about their bodies then let them browse a selection of magazines for an hour, before asking them again. Their self esteem had plummeted.

Never before have we been bombarded with so many images of perfection: more and more glossies on the shelves, web sites, digital satellite channels, more and more channels showing music videos 24 hours a day. New technology is also removing the images we see of women even further from reality. Just try finding a cover on the shelves this month where the star has not had her spots removed, the dark circles under her eyes eradicated, the wrinkles smoothed and her waist trimmed.

It is common practice nowadays to 'stretch' women whose legs aren't long enough. One men's magazine currently on the shelves, so the industry gossip has it, has put one star's head on another woman's body - apparently, her original breasts weren't 'spherical enough'.

So women have been conditioned to go to the gym and diet, or if they don't, to feel guilty about it, but that still won't achieve 'cover girl' perfection because you can't be airbrushed in real life. I've seen the models close up: believe me, lots of them have varicose veins, spots, apendectomy scars and, yes, cellulite. Only the 16 year olds don't have fine lines.

The pressure on actresses in Hollywood to be a certain size is enormous. You would think we would have been on pretty safe ground shooting Renee Zellweger, the star of Bridget Jones, for our April cover. I had seen the movie; she was, well, Bridget: curvy, busty, with cellulite and a healthy appetite. On the shoot? She was an American size two (UK six). All the outfits, which were samples - clothes made for the catwalk and fitted on size 8 models - swamped her.

She has turned down the Bridget sequel because it would mean piling on the pounds all over again. Jennifer Aniston admits in the current issue of Vanity Fair that she lost 30lb to get the role of Rachel in Friends. On the rare occasion a star is a 'normal' size, it is very hard getting hold of clothes that will be big enough. None of the samples will fit, so fashion editors have to trawl the stores borrowing off the rails. One of the most beautiful women in the world, Liv Tyler, is a healthy size 12; none of the designers are able to dress her directly from clothes that are on the catwalk.

So did I achieve anything with my campaign? I believe so. One newspaper conducted a survey of high street and designer shops and proved how women over size 12 were not being catered for. High Street stores are now providing a broader range of sizes.

Even better, John Galliano's couture show later that summer featured models of all ages and sizes. After appearing on our cover, Sophie Dahl was chosen for numerous advertising campaigns including those for Versace and Opium. And we were getting there.

In the May issue, we published naked pictures of eight ordinary women, and asked readers to fill in a questionnaire telling us honestly how they feel about the women in the photographs, and about their own bodies. Interestingly, of the respondents so far, all the women say their boyfriends find the size 16 woman the most attractive. The results will be made into a Channel 4 documentary in the autumn.

In the next issue, my final edition as editor, we have on our cover three young women, all a size 12, curvy, imperfect, but very beautiful all the same. On the shoot, it was apparent that Suzanne, Myleene and Kym from Hear'Say were all happy in their own skin. For now. On the Popstars programme, Nasty Nigel had told the girls they should go on a diet. 'Christmas is over,' he said to Kym, 'but the goose is still fat.' How long before the girls start feeling paranoid about their bodies, under the constant pressure of fame, is anybody's guess.

In Britain an estimated 60,000 people, most of them young women, suffer from eating disorders while far greater numbers have an unhealthy relationship with food. Many of them take up smoking or eat diet pills to keep thier weight below a certain level. Of all psychiatric disorders, anorexia has the most fatalities - it is very hard to recover from. I refuse to conform with an industry that could, literally, kill.

It's time for the industry - the photographers, the editors, the casting directors, designers and the advertisers - to wake up and allow women to just be themselves. From the phone calls and letters I received at Marie Claire, I know that women are fed up with feeling needlessly bad about their wobbly bits.