Are you talking about me?

With its thinly veiled portraits of real people, the roman-Ã -clef is an established way for novelists to settle scores. John Walsh probes the latest piece of literary mischief and wonders if he played a part

" Oh, Meenu," says a character in Amanda Craig's new novel, Love in Idleness. "I know you live like a nun, but you must know Ivo. Everyone does. He's famous for being the worst flirt on either side of the Atlantic. You must have heard of the Sponge Lunge." A moment later, we catch sight of the reprobate Ivo Sponge: "Even at a distance, his eyes snapped with a particular liveliness, and perhaps a hardness, too. He was plump and tall, dressed in a crumpled cream suit and a panama hat. A figure out of a Somerset Maugham story, she thought, amused, or perhaps someone not quite at ease in the modern world..."

The character's ambivalent response to the cream-suited lothario in front of her is as nothing to the reaction that Ivo prompts in the real-life literary world. He first appeared in Craig's earlier novel, A Vicious Circle, which caused all kinds of trouble. The book was a vinegary satire on modern London, counterpointing the moral vacuity of Soho media-land with the all-too-real traumas of modern NHS hospitals. And while nobody from the medical world - whether doctor, nurse or patient - claimed to "see themselves" among the dramatis personae, plenty of egomaniacal flesh-and-blood figures from the book world raised voices of protest.

David Sexton, the London Evening Standard's acerbic, saturnine literary editor (and a former beau of Craig's) threatened to sue the publishers over the character of Paul Pinsent, a bitchy critic, whom he felt to be a little too close to home. Several people were accused of being - or claimed to be - Mr Sponge, the louche, amoral, waggish, hat-wearing, not-safe-in-taxis literary charlatan (for about five seconds, I myself was fingered as the inspiration for Ivo - like, in my dreams). They looked at the other characters, with their giveaway names (Merlin Swagg, the media mogul, Ben Gorgle, the portly editor of Grunt magazine, not a million miles from Bill Buford, then editor of Granta), and concluded that everybody in Craig's pages must be drawn from life; that her book was a classic example of the roman-à-clef - a novel in which a portrait of a real-life person is presented under a fictitious name.

They're still at it. In Love in Idleness, a romantico-satiric story of British and American middle-class achievers sharing a holiday in Umbria and falling under a spell of lurve - sort of A Midsummer Night's Dream with added mobile phones - Ivo is back as the shambolic love-object at whom all the women throw themselves. But now, he's no longer a mere hack, he's the film critic of a magazine. Which is why Ms Craig got a phone call the other day from a former friend who recently married the film critic of a famous journal. "I hope you're not suggesting for a moment," she said, with a nitric fume in her voice, "that Philip is Ivo Sponge..."

Lord, what trouble romans-à-clef cause, and how we love them. The phrase means literally "a novel with a key", and when they first appeared, in 17th-century France, you could buy an actual "key" that unlocked a book's secrets - a who's-really-who crib published separately. Many people attribute the first such novels to Madeleine de Scudéry, a writer of enormously long, breathy, aristocratic farthingale-rippers (Artamène, ou le Grand Cyrus; Clélie, histoire romaine), which featured real characters and detailed references to the court of Louis XIV.

Probably the earliest British exponent of the genre was Jonathan Swift, whose A Tale of a Tub concerned three brothers thinly disguised as Martin Luther, John Calvin and the Roman Catholic Church. His contemporary, Mrs Mary Manley, published The New Atalantis in 1709, an attack on Whig politicians and famous figures, which brazenly carried a "Key to the Characters" in its back pages.

"Key" novels came thick and fast in the 19th century. Dickens put Leigh Hunt, the newspaper editor, into Bleak House as the irritating sponger Harold Skimpole. Nightmare Abbey by Thomas Love Peacock is a droll satire on the Romantic poets, in which Byron, Shelley and Coleridge strike enervated attitudes. In Disraeli's Coningsby, the wealthy Tory grandee Lord Monmouth was a dead ringer for the atrocious real-life Lord Hartford, while the old Jewish sage Sidonia was clearly modelled on Lord Rothschild. Sharp-eyed bookish celebrity-spotters of the time could not fail to notice that the whiskery old writer with the young trophy wife in Cakes and Ale by Somerset Maugham was clearly meant to be Thomas Hardy; nor to see the tubercular features of D H Lawrence peering through the pages of Aldous Huxley's Point Counter Point.

The last decade has seen some exciting examples of the "revenge-à-clef". Not very long after Melvyn Bragg was interviewed in The Independent on Sunday, by Lynn Barber, the scary veteran interrogator, and given a serious roasting ("Smiling, simpering, giggling, exuding his awful smug, matey blokiness..."), he published a novel called Crystal Rooms, which featured a pushy, fortysomething hack called Martha Potter who is portrayed sitting in a public lavatory, pleasuring herself while dreaming of Prince Charles.

Another revenge saga was Harry Ritchie's first novel, Friday Night Club, a comedy of affectation and laddishness set in the offices of The Sunday Chronicle, which is run by the autocratic and ignorant Jonathan Witherington - not a thousand kilometres from The Sunday Times, where Ritchie was literary editor for some years under John Witherow. More recently, the "key-novel" trend has shown signs of a comeback. Gaveston, the debut novel by Stephanie Merritt, deputy literary editor of The Observer, belaboured several celebrities of literary-media-land, most notably the TV smoothie "Mervyn Bland" (way to go, Melvyn Bragg - what has he done to all these ungrateful young writers?) and the blonde-haired People's Poet, Jonathan Friendly, who writes hopeless odes to the extension of the Metropolitan Line.

In American literary circles, authorial feuds and political revelations drive the best romans à clef. Gary Indiana's 1998 novel Resentment: a Comedy was a classic. Set in the media ballyhoo circus surrounding the trial of the Menendez brothers, it took a series of gratuitous swipes at a number of social commentators, especially Dominic Dunne of Vanity Fair, and his equally celebrated brother John Kennedy Dunne, who is married to the legendary Joan Didion. They appeared, pinned and wriggling in the pages, as Fawbus Kennedy, Sean Kennedy and Cora Winchell, constantly preening themselves, concerned about the state of their reputations while "the joke is that all three of them can't get through a paragraph without telling you which famous people they know".

Oooh, bitch bitch. They take these things more seriously in America, however. Rather than worrying whom a character like Ivo Sponge most resembles, their literary gossips wondered which true-life presidential aspirant and which members of his real-life entourage were being scissored in Primary Colors, by Anonymous, the book sensation of 1998. This was the 20th century's climactic novel-with-a-key; its connection to the real world, rather than to the conventions of fiction, gave it an urgency, until the whole of Washington, DC, was talking about it. Rarely has there been such speculation over the real identity of fictional characters.

Something along the same lines is about to break on this side of the Atlantic with the publication of Hard Choices, a political satire by Carol Hayman. Ms Hayman is a former associate director at the Royal Court Theatre in London, whose book has had an extraordinarily chequered history - five years of "rave rejection letters" from major publishing houses (HarperCollins, Penguin, Simon & Schuster) who judged it too savage, too shocking or too libellous to get past the learned friends of Number 10. It's a demolition project on New Labour, involves a conspiracy by the media and a business consortium to put something nasty in the nation's food, and it stars a prime minister called Gideon Price who is caught by his wife doing unspeakable things. Elsewhere, a woman cabinet-minister faces a moral dilemma when she discovers the PM's guilty secret. "It's Clare Short's life story, basically," said Hayman's publisher, cheryl Robson, "but there are all kinds of spooky correspondences. When it was offered to publishers a couple of years ago, there was a different mood in this country towards Tony Blair, and people weren't disposed to criticise. But now - if I told you the book features scientists and dead bodies, ministers being outed and committing suicide... well, it could hardly be more topical."

Being topical isn't, of course, what makes a satire a roman-à-clef - being a recognisable portrait, whether it's of Byron, Bragg, Dunne or Blair, is what gives the novel its teeth. To spend time with a book in order to read scandalous revelations about real-life people is not an elevated or honourable thing to do, but it appeals to the gossip-sharing quidnunc in all of us. Because the thing about fiction is that some or all of it may be based on the truth. And if everything in Primary Colors turned out to be gospel, we can allow ourselves the frisson of wondering if even a fraction of Hayman's horrible "Albion" is Britain today.