Like descriptions of the sexual act itself, the reactions of the writers annually garlanded by the Literary Review's celebrated Bad Sex in Fiction Award can vary wildly. Alan Titchmarsh, grateful for a brief moment of literary glory, hammed up his acceptance speech for all it was worth. The novelist Philip Kerr, on the other hand, I seem to remember being slow-hand-clapped by the audience as he lectured the judges for their effrontery. Quite what the late Norman Mailer's reaction might have been to this posthumously conferred honour we can only guess he died a fortnight before this Tuesday's ceremony but there is at least a chance that it would match his legendary response to the sailors who, while Mailer was out walking his poodles in New York, supposedly "accused my dog of being a queer", thereby precipitating one of the great Mailer punch-ups.

Amid all the hilarity about Jeanette Winterson's robotic love-romps and Christopher Rush's cod-Shakespearian paeans to "glorious pubes! The ultimate triangle", the Bad Sex award, founded 15 years ago by the late Auberon Waugh, is there to make a perfectly serious literary point. This is not just that writing about sex has always been one of the most difficult tasks facing any novelist in any age, but that it has become even more problematic since the opening of the early 1960s floodgates, when, after the Lady Chatterley trial, it was finally possible to address the subject in any way you chose without finding your book turned down by a nervous publisher, disparaged by a moralising newspaper or banned from the library shelves by a vengeful watch committee.

As to why the chance to write about sex in conditions of absolute well, more or less absolute artistic freedom should have produced so many monumentally awful pieces of sub-erotic prose of the kind submitted to the Literary Review, one need only look at the techniques in use before the Chatterley dispensation. Becky Sharp in Vanity Fair, for example, is one of the great sexy heroines, and yet the really striking thing about her is how obliquely Thackeray conveys her allure just a few glancing accounts of her long white arms and "famous frontal development". Significantly, Reese Witherspoon, cast as Becky in Mira Nair's recent film adaptation, played her as a routine sex-bomb-cum-exotic-dancer, and the effect was horribly inauthentic. The same air of intense eroticism, discreetly channelled, glows through the modernist fiction of the inter-war era. There is a wonderful ship-board seduction in Anthony Powell's Venusberg (1932), for instance, in which, their business concluded, the hero tells his mistress that she has forgotten "this". "This", you infer, is a vital undergarment, but the reader never knows, and the frisson is all the stronger for the lack of revelation.

Powell's opinion was that any novelist with an ear for dialogue and an eye for stage direction could get round the prohibitions of the pre-Chatterley era, and that in some cases they worked in the novelist's favour, by encouraging him or her to look at stock situations in different ways. Certainly, most of the novelists given their sexual freedom in the 1960s had no idea how to use it. To examine some of the "classic" English novels of that decade, when most serious writers had got the sexual bit between their teeth, is to be struck not so much by the comparative novelty of the descriptions and the language, but by the beetle-browed earnestness with which they set to work.

But at the heart of the novelist's difficulties with girls and boys lies a single, procedural dead-end. Like sport, sex to the vast majority of people who write about it is essentially a romantic activity. At the same time, also like sport, any attempt to pin it down on the page, by a chronicler who generally considers himself a "realist", will nearly always be compromised by the importation of unromantic physical detail. AS Byatt writes convincingly about sex by majoring on incongruity, awkwardness, incidental comedy. Far more usual, though, is the line taken by a novel like Ian McEwan's On Chesil Beach. The premise may be romantic two young people who love each other approaching their wedding night but McEwan's lemur-eyed interest in the male half's genitalia has the effect of making the reader feel that Russ Meyer has just sat down to write a treatment of Gray's Anatomy.

In nine cases out of 10, consequently, the reader who sighs mournfully over the sex scenes with which most modern fiction is liberally sprinkled is not being prudish but simply responding to bad art. George Orwell, who lived to see a certain amount of the pre-Chatterley stirrings, thought that the modern novel's obsession with sex was merely another of its incremental phases, and that in a century's time we would regard frenzied on-page couplings in the same way as the extended death-bed scenes of the Victorian three-decker. For the reader nervously reconnoitring Winterson's amorous android and the withered organ in Mailer's The Castle in the Forest "soft as a coil of excrement", that day can't come soon enough.