There's been an uneasy consensus among reviewers of Edmund White's new autobiographical memoir, My Lives. Most have found its sexual explicitness difficult to take but have in the end felt compelled to acknowledge and often admire the extreme honesty of a subtle and knowing writer, who, in Gilbert Adair's words, has chosen to spend so much of his adult life in "slavishly obsessive thrall to the male sexual organ". My Lives is not all sex. White finds time to tell us a great deal about his claustrophobic parents, his eccentric psychiatrists, his long sojourn in France, and his famous friends. But when I was preparing to interview him I knew that at some point I was going to have to confront a range of extreme sexual behaviour that I found not only alien to my straight viewpoint but also difficult to reconcile with a humanist stance.

Explicit sex is nothing new in White's writing. We seemed to have learned everything we might want to know about his sex life from his autobiographical tetralogy: A Boy's Own Story (1982), The Beautiful Room is Empty (1988), The Farewell Symphony (1997) and The Married Man (2000). With all that confessional background this latest venture struck one as rather like Proust turning up at the end of his life and announcing that he was now going to tell us how he really got on with his mother.

White affably disagreed with my analogy. "Well, I wrote a little book about Proust in which I noticed how much he had really invented. He would sometimes write letters to friends and ask if they had read his autobiography meaning his novel, but that was complete rubbish because he invented everything. His work was based loosely on his life. But not in any very exact way. And my own autobiographical fiction is also quite far from my actual experience. For instance in A Boy's Own Story, if I had made the boy as eccentric as I really was then nobody would have been able to identify with him. I was really quite precocious, both sexually and intellectually, so I sort of dumbed down the boy in the story and tried to make him a little more innocent than I was."

But didn't this turn away from fiction create a further problem? Most writers who wanted to be biographically explicit employed fiction because it provided them with the perfect get-out. It's only a story, stupid. But he now had no such alibi. All the names and the facts were on parade. It was a degree of explicitness which had led one reviewer to complain: "Although Edmund White is HIV positive, the riskiest thing about going to bed with him… is that your most intimate details – your dimensions, your distinctions and your defects – will sooner or later be writ large for all to see." Wasn't that a high price to pay?

"Maybe I have been unwise to unveil so much. But I did feel that people's lives are made up of such disparate elements that you almost never see thrown together in fiction or in autobiography. I know so many New Yorkers who will go directly from the opera in their black tie to some sordid partouse. It seems to me that so many people's lives are made up of so many funny different elements and I wanted to put them together. To juxtapose those elements which you seldom find rubbing shoulders."

But didn't that make his revelations sound far too innocuous? My Lives was less a comedy of manners, a compendium of sexual hypocrisies, than an anatomy lesson in the outer bounds of gay sexuality. I read an extract that I had underlined. "The basement level… was dank and narrow and smelled of cat piss. T ordered me to kneel on all fours facing the wall. When I heard him rooting around looking for a rubber and lubricant… I glanced back over my shoulder. Furious, he sprang forward and beat my ass with my belt: 'I told you to fuckin' stare at the wall, shithead'. A minute later he'd unrolled the rubber and was slamming his way inside me."

Wasn't there a danger that such frankness might even alienate some of his gay admirers? Did they want to know about a life that might be so much more sex-obsessed than their own?

"Well, I was writing about myself. What else can I do? I can't pretend. Anyway, what is too much sex? Somebody once said that someone who is having too much sex is someone who is having more sex than you are. That is so relevant. I once figured out that I had had about 3000 partners."

I was not about to question his figures. I'd done quite enough background reading on White and the gay movement in America to know that promiscuity on this industrial scale could be regarded as evidence of a thoroughgoing subscription to gay ideology. It was, as John Banville, the Irish novelist, pointed out in a recent review of White's work, a revelation that was brought about by the arrival of the Aids epidemic: "Before that we did not know, or averted our minds from the knowledge, that in the course of their active lives a large number of gay men will have thousands of sexual encounters, many of them anonymous and, it must also be assumed, loveless, though not, it must also be assumed, joyless." What the straight world also had to learn, Banville went on, was that in the gay world "having as much sex, as often as possible, with as many partners as one can accommodate, represented for the gays of the 1970s what White's narrator in The Farewell Symphony describes as a 'noble experiment'. It was a belief which, in the words of sociologist, Alan Sinfield, depended on the argument that since sex is what the system had tried to stop gays doing, then 'the more sex we have the more we assert our gayness'. White, himself, has announced on more than one occasion that sex is 'worth dying for'."

It is a difficult position to defend but White is consistently unrepentant. "Even though I was criticised for 'glamourising' sexual promiscuity in The Farewell Symphony, my own feeling is – wait a minute: everyone dies in the book. So it's not denying or ignoring the consequences of unsafe sex."

White speaks with authority on Aids. He found out that he was HIV positive in 1985 and had to watch his friends and lovers die sad ugly deaths. When he learned about his own condition he "pulled the covers over [his] head for a year and didn't do anything", but later he learned that he was a 'slow progressor' and might still have many years to live.

Hadn't his lucky escape made him just a little more cautious, a little more sympathetic to those gays who now stressed the safety of coupledom, the security of marriage?

"There's been a weird natural selection whereby the people with my beliefs tend to have died. And the people who are cautious and prudish and pleasurephobic are the ones who survived, so you hear a lot from them. They preach to everybody and give a lot of lessons.... I'm very pro-pleasure but I don't think that makes me irresponsible."

He certainly doesn't want to be shunted into coupledom. He's not even certain that coupledom is safer than the promiscuous life he likes to lead. "My own feeling is that it's better to go into a back room and have safe sex with 20 unknown people than have unsafe sex with your lover – because you can't really believe what he says."

Neither is White's insistence upon the distinctiveness of gay love and promiscuity merely a behavioural advocacy. He believes that by writing so honestly about the nature of such sexuality he is reviving fiction. "I was so thrilled when I read in a book called U and I by Nicholson Baker (the American novelist and critic) that he felt heterosexual novelists were now being outstripped by gay novels in terms of frankness and in terms of examining the perverse aspects of love. All the arbitrary aspects of the gender role. I really do think the romantic and the social novel have got a shot in the arm from a new approach."

I suggested to him that one of the most original aspects of human relationships which 'gay novels' such as his own highlighted was the distinction between friends and lovers. To a straight reader like myself this was almost the most uncomfortable aspect of his fiction. Why did lovers and friends have to be so dichotomised? "Well, sometimes friends can become lovers. If you have a real friend you just wish good things for him and you want to do everything that will make him happy. And I don't think you have that attitude towards a lover. You would say to a friend, 'Look, if you are interested in him then go ahead and do it', but would you do that with a lover?"

But wasn't there something anti-humanistic about the manner in which so many of the sexual encounters in his novels and his life depended on the depersonalisation of the lover. We are given intimate details about the texture of his skin, the lustre of his hair, the shape of his cock, but nowhere are we allowed to know anything about the person. Lovers, in White's world, are truly sex objects.

"Well, I think there is esteem love, where you really esteem the other person and it's very close to friendship. But there is also passion which is depersonalised. Did Tristram really care about Isolde's hobbies and childhood? When Phaedra falls in love with her stepson is she really hoping that he will do well in school next semester. Love is a terrible urgent burning destructive force."

Did this mean that straight people were merely fooling themselves with the notion that love and friendship could be congruent? Were they engaged in a rationalisation that his gay writing would help to dispel?

"It's not gay/straight. It's about men and women. The thing about gay male life is that it is men on men. It's male culture which is untrammelled or unresponsive to female culture. I remember reading a study of various kinds of couples in their mid-30s. It seemed that lesbian couples had sex once a week. The male gay couples had it three times a day. And the heterosexuals twice a week. So, you can see heterosexuality as a kind of compromise between female desires and male desires. But when you have two men together they are much more direct about desire, much more spontaneous about it."

There's no time for friendship amongst all that desire? "I wouldn't want to exclude friendship from gay male life or even gay male love. What often happens when passion dies away is that friendship is left. What is really remarkable about gay male life is that gay male lovers usually remain friends. I can't say that about heterosexual couples after they break up."

But even if one accepted that such insights as these might add some variation and extra subtlety to the average novel about relationships, did this mean that one wanted to champion a gay genre of fiction? Wasn't the acceptance of the gay label a way of circumscribing one's sexual behaviour that the true seeker of sexual pleasure would find constricting? He must surely have heard this sort of argument from his discussions with his one-time friend, Michel Foucault?

"Well, he wasn't very good value as an intellectual companion because he didn't like to talk about ideas. The first time I ever had dinner with him was in New York and I thought 'what am I going to say to him?' I eventually said, 'How did you get to be so smart?', and he said, 'You know, I wasn't always so smart. I was a very bad student and then one day I fell in love with this boy who was even dumber than I was and I thought I could ingratiate myself with him if I did his homework. So I began to study so I could do his homework and that gave me a taste for it. I was madly in love with him. And then forty years later I was on a train going back to Paris and there was another old classmate of mine who started talking about school. I didn't mention my boy's name because I thought even at age 50 that I would blush. But I finally asked, "What ever happened to Jean Pierre?" And he said, "That old fag?" "Why do you call him that?" "Oh well, we all had him. Didn't you?"."

A good story. But what about my question? Did the great French philosopher approve of White's decision to describe his writing as 'gay fiction'? White smiled. "Well, I think he thought that gay photography or gay painting was nonsensical but gay fiction was at least interesting because it showed people working out how to live in gay relationships. It was an ongoing project because nobody quite knew how to do it. He didn't mind people referring to homosexual acts but he didn't like the fact that they would say that they themselves were gay. He felt that we had inherited one bad thing from Christianity and that was the culture of avowal, the confession. You confess your secret on Jerry Springer and then you are defined for all time. I think he found that very trivialising and essentialising."

"But aren't you guilty of just that essentialising in many of your books? Aren't you forever insisting there are such 'things' as gay people and gay sexuality?"

"I recognise that. I have a chapter in My Lives called 'My Women' where I talk about all my early experiences with women and how I think if I was actually born in a more benign age, let's say a late one which had been more influenced by Foucault's de-classification of sexual orientation, then maybe I would have been bi-sexual rather than exclusively one thing or the other."

We'd stayed off the subject of age until this point, even though White's descriptions of himself in My Lives as fat and old and increasingly pathetic are terrifying examples of the frontiers which this exercise in self-exposure chooses to cross.

I asked him if he hadn't brought such self-disgust upon himself because of his own obsession with physical beauty and particularly with the romantic argument that physical beauty was always a promise of real beauty, beauty with a capital 'B', an argument that his detractors had crudely labelled 'lookism'?

"Well, at the time I wrote that I had just had my heart broken by a young lover, a karate champion who was and is quite beautiful. And I guess I was a little bit melancholy but I have come out of that and I have met a few people. I still feel in the swim. It seems like people are infinitely varied and you can always find someone who wants what you have to offer. I mean it is awfully hard to grow old, not just because you are losing your looks, but because you are bored with yourself, bored with your life, with how predictable others are, because you know in another ten or 15 years you will be dead. As my mother said, 'Nobody gets out of this thing alive'."

White lives by that sentiment. He is firmly in the present and wants to tell the world that this is main lesson of the Aids epidemic. "I keep asking: why did I, who'd already lived a wonderfully full life and accomplished so much of what I'd set out to do, gain a stay of execution, whereas Hubert, my lover, who was just starting out in life… had to die at 33?"

"If I were a believer, perhaps I'd have some answers. As an atheist, I can't even imagine that I was spared so that I wouldn't die a fool or a sinner. An atheist lives in the present, since there will be no eternity…Perhaps that's why I was given so much of the present to work with, since it's all I'll be getting."

One last fascinating footnote. Although I didn't know it at the time of my interview, White's new book has not yet been released in his native America. Apparently the publishers wanted to find out how its explicitness went down in the UK before risking their reputation in the States. As I can personally confirm, at the grand age of 65, Edmund White is still frightening the liberals.

Thanks to the Times Literary Supplement for helping secure this interview