This magazine for men sells 775,000 copies a month. These magazines for men don't. Spot the difference. (Sad, isn't it?)

It was revealed last week that editorial executives at the American magazine Movieline had vetoed a cover in which a portion of Elizabeth Hurley's left buttock was seen peeking from beneath a fur wrap. This was too shocking for American sensibilities. So the tremulous suits were concerned they would lose their jobs if La Hurley's bare skin was revealed on their cover.

In this country we do things rather differently. In this country, a publishing executive would lose their job if their magazine possessed nudie shots of Our Liz and didn't bung them straight on the cover. That, after all, is what covers are for, which is why the current edition of Tatler has a naked Anthea Turner beaming from its front cover, her modesty and nipples protected only by a strategically draped python.

A barely-clad blonde (or Wonderbra'd brunette) is the sine qua non of contemporary publishing and for a very simple reason: she sells. The single most powerful proof of this proposition can be found in the staggering success of the men's magazine FHM. Last week it posted its Audit Bureau of Circulation figure for January to June 1998, which revealed an average monthly sale of 775,451 copies.

This figure represents a rise of 130,000 in the past six months. Already regarded as a triumph, FHM is now becoming a phenomenon, bringing in pounds 2m in sales revenue per month, plus another pounds 500,000 in advertising.

Its nearest rival in the men's market, Loaded, sells 456,373 per month - up a respectable 15,000 in the past six months, but still way behind a publication that was once seen as a "me-too" title, trying to cash in on the New Lad market Loaded had created.

To get a sense of the scale of FHM's success, compare it with the glossy magazines aimed at women of the same 16-25 age range. It has long been an article of publishing faith that men would never buy magazines in the same numbers as their female contemporaries, and until very recently that dogma was supported by the facts. No longer. FHM's female equivalents trail far behind: Cosmopolitan sells 472,263 per month, Marie Claire 416,239. As for the posh mags, FHM sells twice as many as Vogue, Tatler and Harper's & Queen ... combined. The magazine's editor, Ed Needham, has the confidence of a man who knows he has the Right Stuff. "We are standing on a mountain and still looking at a peak obscured by clouds. There has to be a finite number of readers, but no one knows how big the market is."

So what's the secret? Well, it certainly isn't fine writing. All those men who for years excused themselves by saying that they bought Playboy for the articles could at least point to the quality of the magazine's contributors and the astonishing fame and power of its interviewees. But FHM has no such pretences. Its occasional big(ish) stories - self-consciously "hard" tales of violence and crime - are basic tales for basic blokes. They nestle amongst hordes of snappy how-to features, laddish columns, photo-spreads of stuff to buy, advice (well-meaning and very useful to its post-adolescent audience) about sex, emotions and health ... Oh, and girls. Let's not forget girls.

FHM has the best crumpet in the business. If you want to see the most scrumptious pics of the Playboy model-turned-TV-hostess Jenny McCarthy - her silicone breasts straining the skimpy fabric of her bra, a barely- discernible shadow of pubic hair just visible beneath her gusset - FHM (April 1998, if you're interested, lads) is the place to look. If you want Denise Van Outen in her undies; Melanie Sykes in her undies; Denise, and Melanie, and Davina McCall, and Jenny Powell, and Melinda Messenger, and Tania Bryer and Donna Air, all in their undies ... in the same picture ... then FHM is your kind of publication. And if you're wondering who on earth these young women are, then clearly you aren't in FHM's target market. Because if you were a hormonally-supercharged 19-year-old male with a taste for trash TV, you'd know all right.

FHM have a girl on the cover of every edition. Other magazines do not. Loaded, for example, occasionally deviates from the female formula in favour of some suitably iconic male: a footballer, or hard-nut actor. This may explain why their sales are so far behind FHM's. That, and the tangy odour of smut that wafts around Loaded, always the naughtiest boy's mag around.

Loaded girls look dirty. But FHM is an entirely respectable alternative to the porn rags and jazz-mags whose sticky pages used to be hidden under every teenage boy's bed (and whose own circulations are now so desperately flaccid). You can take FHM home to your mum. Or she can buy it for you the next time she's in Sainsbury's.

The fact that there is no cover-man a man will buy ahead of any pretty cover-girl has been proved to most editors' satisfaction by their market research. Eighteen months ago, Esquire was running covers featuring men like Liam Gallagher and Robert de Niro. But the new editor, Peter Howarth, quickly realised that he was going to have to swim with the totty tide: he could maintain his magazine's literary standards on the inside, but the outside had to boast a babe.

That's why this month's Esquire features Melanie Sykes, while last month's had three "babes in the bed", one of whom was Denise Van Outen, who had also been on February's cover. You may now be noticing a certain repetition here: no matter what the magazine, the girls are all the same.

So a problem arises: if the magazines all have girls, and the girls are all the same, how can you tell the magazines apart? Well, says Peter Howarth, that's a matter of style: "Our cover girl will be shot in something by Prada or Gucci, rather than something by Gossard or Anne Summers, and therein lies the difference."

Quite so, but there are only so many girls who look good in either Gucci or Gossard, and competition is fierce between rival titles as they try to snap them up and outwit their competitors. "You get to know what photo shoots have been taken," says FHM's Ed Needham, "but that doesn't mean we know when they will appear. There are ways of finding out what other magazines will have on the front, but we don't use them."

But what happens if the supply of girls runs out? Already this year, GQ have run a cover featuring Daniela Pestova, an absolutely ravishing Czech model whose sole claim to fame is that, well ... she's married to this bloke who owns the Fashion Cafe. One glance is enough to tell you why men would want to look at her. But would they want to buy a magazine just because of her? The evidence suggests not: GQ's circulation actually fell during the last six months to 130,152. And there's something else: why would Daniela - let alone a genuine celebrity - want to be looked at?

This might seem like a crashingly obvious question - answer: because she wants to be rich and famous, stupid - were it not for the fact that the phenomenon is so new. In the Seventies and Eighties, no woman who wanted a serious career on television would have dreamed of taking any of her clothes off for a magazine, let alone a magazine aimed at men: her credibility would have been destroyed in an instant. Nor would any men's glossy magazine have dared to print such pictures were they available, let alone put them on the cover.

The glossies were desperate to distinguish themselves from the top-shelf titles: they craved respectability. Plus, they were terrified of feminism. When Esquire's Peter Howarth worked at GQ in the early Nineties, "Putting a woman on the cover was a real novelty. If someone like Michelle Pfeiffer was going to appear in a film we'd say, `Wow! Maybe we could do her.' But the cover would be very tasteful and very clothed. There was lots of discussion of the political correctness of what we were doing."

But then Loaded came along, with its unabashed delight in everything that gave men pleasure, and everything changed. Suddenly, Liz Hurley was wearing That Dress and inspiring a generation of It Girls. Eva Herzigova was saying, `Hello, boys' on a myriad posters. And though there were a few complaints about sexism and exploitation, you simply couldn't argue with the numbers. Loaded's circulation exploded past its respectable rivals, Liz became rich, Wonderbra sales went through the roof. And the girls who were buying those bras felt like the exploiters, not the exploited.

At Tatler, Jane Procter never has any problem persuading celebrities to bare all. "Someone suggests it at the shoot, and the girl trusts the photographer, the hairdresser says it would be a good idea, and the fashion editor says, `Your husband will love it'.

"The girls say yes because it's a jolly jape - a bit of a tease. They've got nice bodies, expensive bodies. They've been massaged and exercised down at the Harbour Club and they like showing off."

They love the publicity, too, and glossy magazines make the perfect springboard for nationwide PR. Tabloids will happily reprint the glossies' up-market smut.

When FHM's "100 Women" went on sale it was accompanied by a week of pictures of the women in The Mirror. Each picture was flagged as coming from FHM, which is "on sale now" and the front cover appeared next to every shot.

Similarly, when Loaded celebrated its 50th issue earlier this year, The Sun printed pictures of women from the anniversary issue for five days. The advertising value of a week of shots would have been worth in excess of pounds 200,000.

"Every month I get something in the papers," says Ciara Parkes, who runs Public Eye, Loaded's PR agency. "You have a contract," says Ms Parkes. "If they do not adhere to what I request they are charged for the pictures. The pictures have to run on the day of publication, they have to show the cover, and to a certain size, in colour and they have to write that the magazine is now on sale."

Most of the magazines' PR agencies have strong relationships with one or two newspapers. Much of Loaded seems to go exclusively to The Sun, much of FHM to The Mirror, but PRs will try to keep as many big circulation titles on side as they can. "It is an immensely beneficial relationship for us," says Ed Needham. "We have something they want, and they have 12 million readers we want."

And girls who would never want to be seen collaborating with the tabloids can bare all for a respectable glossy, secure in the knowledge that they'll still get mass-market coverage when the pics are syndicated. Last week Tatler managed to get a naked Anthea Turner into every tabloid newspaper, across the top of page three in The Daily Telegraph and half a page in The Times. The Sun even put her across the top of its front page as well.

The Anthea pictures were an exception. The former Blue Peter presenter requested the papers pay pounds 1,000 to a breast cancer charity for use of the pictures, but usually the use of pictures is free.

"If Anthea had done those [snake] pics in almost any other title, she could have been accused of being tacky," says Jane Procter. Ciara Parkes is not convinced being in Tatler makes much difference: "She might have been trying to manipulate her image by using the magazine brand, but she still took her kit off and ended up in The Sun. It's the same as Ulrika [Jonsson] being in Loaded."

The other great exploiters of tabloid interest are the gossip magazines HELLO! and OK, but given that Anthea Turner's former lover Grant Bovey and his wife made substantial sums from HELLO! and OK, it was also unlikely that she would have given her first interview and pictures to those magazines since they broke up.

But Procter has something else to offer: protection. Pictures are only released to the press under very strict conditions. "We can control their exposure in the tabloids," she explains. "If the girls are not models, they are celebrities, so we have to protect them. If we gave, or sold on, pictures that were used to go with a knocking story we would lose trust in the celebrity world."

Some old-fashioned journalists might wonder if their function in life was really to protect celebrity egos. As one showbusiness reporter comments, "If celebrities start getting copy and picture approval from magazines, they will start to expect it from newspapers. We could create celebrity monsters like they have in the US who want to control everything."

We could. And we could sell what remains of our principles down the river, too. But as long as the sales are so good, will anyone really object? Even the Americans may be changing their ways. Last year the editor of the US men's magazine Details decided that he could learn from his British peers. He ran a cover featuring lingerie-clad TV stars that was an exact copy of an FHM cover. And guess what? In the prudish US of A ... sales went through the roof.