It has been taboo for more than 500 years. But from fcuk to Four Weddings and a Funeral, the f-word has become so commonplace it now seems acceptable in everyday conversation. Is it no longer obscene? And if it isn't, what is? Jonathan Margolis investigates

The first time I heard the word fuck, I was seven. My 12-year-old brother asked me if I wanted to know the worst word in the world. He whispered it to me and, although he wasn't quite sure what it meant, we both loved the idea of a word so rude that it could barely be uttered.

And in suburbia in the 60s, you would not even breathe such a word. I know my parents were aware of it from the war, and it was certainly in their secreted-away 1962 Penguin edition of Lady Chatterley. But whereas today, any 12-year-old from the dodgiest comp to Eton would say fuck if they so much as grazed a knee, I doubt my dad would have said it even if a flying saucer landed on the patio and a Martian laser-gunned the shed.

It wasn't until 1970, when I briefly encountered that rare bird in Ilford, Essex, a television director, that I realised it may indeed have been the worst word in the world for lower-middle-class people like us, but for the educated middle class, it was in everyday use.

The television bloke had been filming an item for BBC Nationwide nearby and asked to use our phone. My mother was clearly enchanted by him. He had long hair, the first pink shirt we had ever seen on a man, and said fuck several times in a brief call to his producer. My mum, who had ideas above her station, seemed to resolve from that moment to say fuck several times a day as a way of showing that she was moving onwards and upwards.

Three decades on, the word is so commonplace that its shock value seems quite lost. Kenneth Tynan saying it for the first time on television in 1965 caused considerable scandal, albeit without mention anywhere of what he said. (It was: "I doubt if there are any rational people to whom the word fuck would be particularly diabolical, revolting or totally forbidden.")

We didn't know it in Ilford, but by the time our trendy television man was using fuck so casually, the middle-class (or at least literary) hijacking of the word from workmen's slang was well underway. DH Lawrence, James Joyce, Henry Miller and Dylan Thomas had started the process, and now Doris Lessing, WH Auden, William Burroughs, John Updike and Iris Murdoch were joyously embracing the word. Soon, the speech of barristers, cabinet ministers, academics and surgeons was splattered with fucks, as it still is today when they want to appear unsnobbish. And, paradoxically, it is often ill-educated people who are the more loath to say it - for fear of appearing ill-educated.

In 1976, the Sex Pistols famously used the word on Thames Today, infuriating presenter Bill Grundy. And from the 1980s onwards, films have routinely contained a fusillade of fucks, with Hugh Grant's opening salvo in Four Weddings and a Funeral a notable example. Which made it little surprise that by 1997, when several broadcasting organisations produced a ranking of words by severity, fuck only came in third, behind cunt and motherfucker.

If evidence were required that the word has in some sense come of age, the clothing company French Connection has recently opened a giant FCUK store almost next to Harrods. A pseudo-anarchic gesture that would once have been the subject of anger and sensation, today this is not even noteworthy enough to be a bore. It is a true non-event.

Why did fuck lose its sting? Has its diminution left us bereft of a useful, powerful expletive? If it has, is language the poorer for its emasculation? And is there an unspoken agenda that it is still rude when the speaker is working class? Or if it is used in a work of art, such as this year's Gilbert and George exhibition, The Dirty Words Pictures, 1977?

There is a pervasive myth that in some hey-nonny-no idyll of yore, the word was lusty language, but not obscene. But according to Jesse Sheidlower, the author of the 1995 American book, The F Word, fuck, which seems first to have appeared in a 1475 manuscript satirising the monks of Ely Cathedral ("They, that are the monks of Ely, they are not in Heaven because they fuck the wives of Ely"), was always taboo. This was the case even though shit, which dates to the ninth century, was perfectly acceptable.

So the softening of the word is entirely a modern business. And for Charles Jones, professor of English language at Edinburgh University, it is no longer necessarily a swear word, and barely an incivility. Jones gave evidence last year that helped Kenneth Kinnaird of Glasgow successfully appeal against a breach of the peace conviction after Kinnaird told an Edinburgh traffic policeman to fuck off. Lord Prosser agreed that Kinnaird, 43, was only using the "language of his generation".

"For many working-class men, fuck seems to me hardly countable as an expletive," says Jones. "Rather it is used as a reinforcing adverb: 'It's fucking cold/hot/terrible' or whatever. Some purists argue that this shows an inability on the part of these speakers to use (or even to have) more sophisticated vocabulary, but I doubt this. In my view, nothing is regrettable in linguistic usage."

John Ayto, editor of the Oxford Dictionary of Slang, concurs on the de-sexing of fuck. "Fuck is a sexual term but realistically, it is almost never used that way. The overwhelming amount of times it is being used in some figurative sense - 'I'm fucking tired' or 'We got fucked on that deal'. I think it would be too much to say that fuck doesn't offend anybody. It hasn't finished the journey yet to becoming a milk-and-water word. But its impact is diminishing at a rapid rate. Young people tend not to think of it as offensive at all."

The decline is a matter of shifting taboos, says Jean Aitchison, the Oxford professor of language and communication who is married to Ayto. "In the last century, it was religious swearing that upset people," she says. "Then, in the mid-20th century, sexual swearing. But these days people get far more upset about politically incorrect language: nigger, and even mad, are quite taboo. Most kids say fuck a lot, but haven't a clue what it means. They just know it gets adults upset, and so keep saying it - and I have upset teachers in the past by saying, 'Why don't you just ignore pupils who say fuck? They'll soon get tired if they get no response.'"

"Ethnic slurs are regarded as the taboo," agrees Ayto. "Nigger is far more taboo than fuck or even cunt. I think if a politician were to be heard off-camera saying fuck, it would be trivial, but if he said nigger, that would be the end of his career."

Further verification that fuck is, well, fucked, comes from Andrea Wills, the BBC's chief advisor on editorial policy. "In research, 50% or more people said the words that should never be broadcast are cunt, motherfucker, nigger, Paki and spastic. Young women also don't like whore, slag and twat. But fuck wasn't on the list."

So not-on-the-list is it today, that Aitchison tells this story. "A child upset its grandma by saying 'fucking knickers'. The child's mother said, 'Don't ever let me hear you say that in front of grandma again'. The child's response? 'When grandma's here, should I say 'fucking trousers?'"

As well as liberalisation for its own sake, the fact has also dawned that, linguistically, fuck is a very flexible and interesting word. According to an internet wit called Nick Lohr, who has an audiovisual tribute to fuck at www.fuck.addr.com/news/word/larry.html, we would all do well to use the word more in our speech. It is, he contends, "the one magical word which just by its sound can describe pain, pleasure, hate and love - fuck falls into many grammatical categories, as a transitive verb, for instance: 'John fucked Shirley.' As an intransitive verb: 'Shirley fucks.' It's meaning is not always sexual; it can be used as an adjective, such as 'John is doing all the fucking work'; as part of an adverb: 'Shirley talks too fucking much'; as an adverb enhancing an adjective: 'Shirley is fucking beautiful'; as a noun: 'I don't give a fuck'; as part of a word: 'abso-fucking-lutely' or 'in-fucking-credible'; and as almost every word in the sentence: 'Fuck the fucking fuckers.'"

The class issue remains an awkward one for fuck's supporters. The classier the accent, the more endearing (and figurative, rather than aggressive) it somehow sounds. Hugh Grant carried it off with aplomb (and a plum) in Four Weddings and a Funeral, and when a BBC Radio 3 announcer recently let slip a fuck on air, it caused little stir; the same station's drama output is a secret treasury of fucks. Yet when football manager Graham Taylor used it 32 times in a Cutting Edge documentary, it went down rather badly - especially with the popular newspapers, which remain squeamish about any word that might unsettle readers; the Sun even avoids "orgasm". Most non-broadsheets, when it is unavoidable, opt for f**k, which lets them, as Jones puts it, be "daring and prissy simultaneously".

On television, watershed rules on profanity have led to an odd inconsistency. No channel will broadcast the word pre-9pm under any circumstances, even in supposedly realistic dramas such as EastEnders. Yet, even though racially abusive language is generally regarded as more offensive today, it is possible to slip in a proscribed word before the watershed on social reportage grounds.

"In the current climate, racial language is very, very sensitive and one has to tread carefully," says Prash Naik of Channel 4's legal and compliance department. "But nigger and Paki are not prohibited pre-9pm. If they are used in a social documentary or a socially responsible drama such as Brookside, with an established reputation for tackling difficult subjects, it can then be justified as highlighting the issue of racial discrimination."

Swearing is, it would seem, at a peculiar crossroads. Fuck is thoroughly denatured. Crap, bastard, bugger, sod, shit, bullshit and tosser (although strangely not wanker) are used on daytime television and radio. Religious expletives, such as damn, hell and blimey, once as powerful as fuck, are not even thought of as vaguely impolite. But Ayto is confident that we will survive the suburbanisation of fuck. "I don't think there's any danger of running out of swear words. We will make them up or regard different things as being more shocking and offensive. There will always be a need to strike a blow at convention by using disapproved words."

There will always be divisions, however, over what is disapproved. As one middle-class west London mother said when I mentioned researching this article: "I'd rather my children said fuck than toilet."