In her new film, "8 women", the French icon Catherine Deneuve shares a kiss with her co-star Fanny Ardant. It's not her favourite part of the movie, she tells Matthew Sweet.

One of the less tacky anecdotes that Roger Vadim tells in his memoir, Bardot, Deneuve, Fonda, is set in the stormbound Alpine hotel that he used as a production base for La Bride sur le Cou (1961), a vehicle for the first of his ex-wives. Brigitte Bardot, under the impression that the hotel is about to be sucked into the stratosphere like Dorothy's farmstead in The Wizard of Oz, has just finished drafting her will. She goes looking for her former husband in order to propose that they celebrate the apparently imminent end of the world. Opening the door of the games room, she discovers Vadim and teenage girlfriend, Catherine Deneuve, hunched over the baize: Vadim has removed his shoes and pullover; Deneuve is wearing only her pants and socks. "I can see you're not bored in here", says Bardot. "We're playing strip billiards," explains Vadim.

Deneuve has left it to former lovers and rivals to dine out on such tales. "Discretion", she says, as a waiter spirits away the remains of her lunch, "is part of my character. And if it had been required of me to be more open, I'm not sure I would have stayed in film". As her one-time co-star Gene Kelly says in "Singin' in the Rain" just before we see him in flashback, strumming his uke in a brothel: "I've had one motto which I've always lived by: dignity, always dignity". In Deneuve's case, it might actually be true: indeed, it is one of the reasons why, nearly 40 years after she illuminated Jacques Demy's "Les parapluies de Cherbourg" (1964), she still commands our attention. At 59, her beauty retains its clarity and correctness, even if it now seems to show its workings in the margins. The L'Oréal ads that she fronts are as close as she permits the public to come. "Sometimes, I see people in magazines and I think: why did you do that? Why did you do that photo at home with your child or in your new kitchen? I don't do things for the public. First for me, then for the public. Otherwise you don't belong to yourself".

So, we know that she was born in Paris in 1943; that her sister, Françoise Dorléac was killed in a car crash in 1967; that Vadim and Marcello Mastroianni were the fathers of her children. But Deneuve has always been careful to leave the details to our imaginations. She has worked the same trick on the screen, always knowing how to act as a vehicle for the fantasies of her directors and her audiences without ever seeming to be consumed or eroded by those desires.

Demy made Deneuve's fragile glamour central to the achy pleasures of "Les parapluies de Cherbourg". Roman Polanski made her the epicentre of "Repulsion" (1965), a young woman propelled into psychosis her own fears and cravings. In "Belle de jour" (1967), Luis Buñuel, as old as the century but still driven by fearsome appetites, gave Deneuve her signature role as the chilly blonde bourgeoise who assuages her unhappiness in a brothel. More recent roles as a passion-struck professor in André Téchiné's "Les voleurs" (1996), a frazzled Rosie the Riveter in Lars von Trier's Dancer in the Dark (2000), and the lacquered matriarch of François Ozon's "8 women", which opens today in the UK that she still knows which directors can be trusted to do right by her.

She saw Morvern Callar on Tuesday, just before she was required to roll up at the V Graham Norton studios to drag up as Vera Duckworth and recite innuendoes that, mercifully, she failed to understand, and now Lynne Ramsay is on her hit list. "A wonderful director," she enthuses, tracing something the air with her skinny cigarette. "I would love to meet her".

Deneuve's latest, "8 women", is a game of musical Cluedo, a kitsch murder mystery sequined with production numbers. But it's also a film about what happens when a gaggle of France's most celebrated divas are forced to share a single screen. These women don't just bring their acting, singing and hoofing abilities to the picture: they haul their public and private histories with them. "Most of the time, you have to fight with that", she says. "Directors have got to get actors and actresses to make the audience forget who they are after 15 minutes. But François didn't even try that. He did it the other way round, and decided to use it".

In his pursuit of pleasure, Ozon sometimes used it a bit more freely than Deneuve might have liked. One of the crowning glories of "8 women" is a rip-roaring fight sequence in which Deneuve and Fanny Ardant extend their glossy claws and smack each other about on the shag pile, before finally allowing violence to accede to a full-on snog. It's a triumph of whoop-de-do camp, an art-house take on one of those moments in Dynasty when Joan Collins and Linda Evans tussled in a blur of false eyelashes and Lalique. But the scene also plays a perverse joke upon its participants. Deneuve and Ardant were both the lovers of François Truffaut; Truffaut's penultimate film, "La femme d'à côté" (1981) was inspired by his affair with Deneuve. The female lead was played by Ardant, who, after the film was made, replaced Deneuve as the director's lover, muse and star. In "La femme d'à côté", Gérard Depardieu, as Truffaut's alter ego, Bernard Coudray, launches a violent assault upon Ardant. In "8 women", Ozon has replicated the moment as farce and added a supplementary clue, just in case the reference escapes the audience.

"In the scene", states Deneuve, "I say a line that I said in a Truffaut film". And how did she feel about that? "Not too good. I accepted to do it but I never felt very at ease. I know for Ozon it was a homage, but I'm not sure Truffaut would have liked it. It's not my favourite moment in the film".

Did she find it disrespectful? "No", she says, "intrusive".

And the kiss with her lover's lover? "We didn't do the kiss many times", she says, in a muted voice. But she cackles with delight when I ask her if the scene has pleased her army of lesbian fans, who continue to daydream loyally about her, despite her 1996 legal action against a US lesbian magazine that was established under her name without asking her permission. She acquired this following Tony Scott's vampire flick "The hunger" (1983), in which she played a fanged seductress, all Eighties hair-gel and flashing eyes, who took her sweet time getting to Susan Sarandon's jugular but such roles have always pleased Deneuve.

In "Zig Zig" (1974) she enjoyed a flirtatious relationship with Bernadette Lafont, one half of a Dietrich-style cabaret act; in "Ecoute voir" (1978), she played a private eye who kissed Anne Parillaud; in André Téchiné's "Les voleurs" (1996), she was an academic who found herself falling in love with a female student (her bathtub scene with Laurence Côte was a model of taste). "When I did "Les voleurs", American journalists told me that an actress couldn't do such a role in an American film. Even an icon like Meryl Streep [who shares a bed, but little else, with Allison Janney in her imminent movie, "The hours"] had to wait a certain amount of time. Maybe today they have let her do it, but 20 years ago would not have got away with a part like that even if she had wanted to. And I'm sure she would have wanted to".

Deneuve slips on her sunglasses, hardly necessary in a restaurant in November, a discreet signal that the interview will soon be over. "We are in Europe. It's very different in Europe, you have more freedom to experiment with who you are and what you do. You're allowed to really play, you know the screen, I have the chance to do things that I wouldn't dare to do in life".

Writing her memoirs falls into the latter category. "I've been asked", she admits, "but very quickly afterwards I said no, no, no, no. If I could write a book like Louise Brooks's Lulu in Hollywood, then maybe I would. But my story doesn't belong only to me. I write it in my diary, but to publish it would be too easy to hurt people. And the pain you've done to someone cannot be undone".

Perhaps she's thinking of Vadim's overdetailed description of what she was like in bed. Perhaps she is cautioned by the the toxic spill of Brigitte Bardot's autobiography, "Initiales BB" (1996), a book that features nothing so innocent as a game of strip billiards.

The two women were often spoken of in the same breath, particularly by Roger Vadim, but they no longer have anything in common. Bardot has disappeared into a frowsty seclusion from which she occasionally emerges to spit at veal farmers or immigrants. Deneuve has remained on the screen with her majesty and her dignity intact. She could have settled down with a big advance and committed real thoughts about her sister, about Truffaut, about Ardant, to print. But that would have destroyed her discreet charm, dispelled the fantasies that she has permitted us to weave around her image.

"Of course, you would want to read it if you had it..." Deneuve says, "but I also think that you would be terribly disappointed. Wouldn't you?"