As he speaks, Erick Zonca is picking at his tarte au citron. "Without my alcoholism, this film would not have been made," he says. (I'd have quite liked wine with my escalope du saumon, but it didn't seem appropriate.) "I've had some really bad problems with drinking that drove me to Alcoholics Anonymous. And when I started attending those meetings I came across some of the stories and characters that appear in this film."

Zonca is talking about Julia, his first English-language film, about a sociopathic alcoholic in which Tilda Swinton gives one of those clamorous, lurid performances that will drive some to throw awards at her feet and others to flee the cinema in search of a stiff one. "What I really wanted to do is make a film about how alcoholism takes you away from the real, you see," he says. "The problem with alcoholics is that the significance of life disappears for them.

"But I didn't want to make a film like Leaving Las Vegas [Mike Figgis's hallucinatory 1995 depiction of an alcoholic drinking himself to death], even though I really admire it, because it is so devoid of that energy that I associate with drinking. I wanted to speak about all that dissociation from the real that I saw in other alcoholics and in myself, but I didn't want to make a sad, morose picture. I wanted a thing with life, you know?

"My grandfather was an alcoholic, too. But he was filled with energy - doing card tricks, telling jokes. He was a funny guy. He would tell his wife that he was going out to get bread for dinner then he would disappear for three days. I wanted to bring that energy to the screen. You don't see that very much when alcoholism is shown in cinema."

Zonca, 52, is best known for The Dream Life of Angels, his critically feted 1998 film about two young French women from the margins of society, but he hasn't made a picture since Le Petit Voleur in 1999. Is that almost decade-long gap in his cinematic oeuvre because of the drink problems? "No, it's because of the money problems. It's very hard to find money to make the kind of movies I want to make."

Good point. Julia is a bizarre film project that might well make conventional producers queasy. It is an existential kidnap caper movie set in LA, New Mexico and Tijuana, and stars an arty British thesp playing what one critic called "a swaggering floozy with a monumental drink problem". It was made with an alienated American crew ("They really were a pain in the ass," says Zonca. "They had no idea what they were filming") and a director rewriting the script with his co-scenarist on set. Zonca couldn't raise American money for the project, which was ultimately bankrolled by France's Studio Canal. But Studio Canal cut the budget by a third one month before the shoot. According to Swinton, she lost weight owing to the pressures of filming in straitened circumstances.

Some critics have compared the resulting film to John Cassavetes' Gloria, seeing Swinton as a latter-day Gena Rowlands. "I'm very happy with the Cassavetes comparison," Zomca says. "I was watching Opening Night and Killing of a Chinese Bookie while I was working on the film. Not because I wanted to copy them, but because the way he shoots things without close ups and in long takes is something I aspire to do." Others, however, were less kind. The trade-magazine critics trashed the picture when it was shown at the Berlin film festival, saying there is no place in the world - at least not in American cinemas - for a 144-minute picture edited down from its original four-hour running time with such a thoroughly unlikable central character. Variety's critic suggested Julia was a "startling misfire" that "uncomfortably welds arthouse sensibilities with genre tropes". Stateside chances are negligible for this English-language flick, he predicted.

"We will see," says Zonca. "It hasn't been released in the US yet, but it has done well so far in France and Germany." Hasn't the hostile critical reaction hurt? "It doesn't hurt because I know I've made a good film. But Variety's review screwed up our chances of distribution deals in the States and even in Europe for a while. Only when people had forgotten about it could we get the film sold."

Why did Zonca want the very British Swinton to play a very American boozehound? "That long lithe body with small breasts, long legs, red hair and pale complexion. I knew that was the woman I wanted in my film for years before I filmed her."

And he got her. Swinton said yes very quickly after she read the script. But there was a problem. "The thing about Tilda is that she doesn't drink," says Zonca. "Well, that's not quite right," says Zonca's co-writer Aude Py, who joins us for coffee. "She can't drink: she has a glass of wine and then falls asleep."

Wasn't casting her in the title role a risk then? "Absolutely," says Zonca. "To play a drunk is difficult enough, but to play a drunk when you don't drink is almost impossible. You know how we made it work?" he asks, leaning forward. Not a clue. "She watched me, and learned the gestures from a real hard drinker. You know in the film, when she wakes up running her tongue round her dry mouth? She got that from me."

Zonca and Py tell me that Swinton was their first choice. "We wanted her even though we knew that we would find it hard to raise money for the film with her as the star. She is not all that well known, certainly not in France which is where we were looking for money." "That's not quite true," says Py, who proves a delightful foil to Zonca. "She's actually well known among intellectual and artistic people here, just not the film producers." "Well, that's the point," says Zonca. "We did think that we should go for a Hollywood name so that we could get the money. We wanted Julianne Moore, who would have been wonderful for the role too. She would have been more expensive."

But we're getting ahead of ourselves. When Zonca and Py sat down in Paris to start writing the screenplay, they knew they were going to write about an alcoholic woman's dissociation from reality, but hardly that they would wind up producing an extremely complicated kidnap flick set in LA. "Originally, we were going to film it in Siberia and New York," says Zonca. "I had this idea of a contrast between permafrost, which is very horizontal, and New York which, as you know, is very vertical." Love that "as you know".

Instead, and probably quite sensibly, the action shifted across the Atlantic. In the script, Julia attends an AA meeting and runs across a satisfyingly unstable mother Elena. Elena suggests to Julia that she kidnaps the son she's not allowed to see. Julia, crazed by alcohol and debts, agrees. She winds up with her son in the boot of her car and has to try ineptly to mastermind ransom negotiations from her motel hideout with the boy's unseen industrialist grandfather."The essential idea that motored the story is that alcoholics are often big liars," Zonca says. "So she lies to the mother. Her idea is to claim the ransom for herself and not give it to the mother. Then she has to lie to the boy so that he is pacified - she keeps telling him she's taking him back to her mother, when really she has no care for him at all. He is just a thing to her."

But isn't she then, as some critics have suggested, irredeemably unlikable? "Not at all. I wanted to make her ultimately learn to care for somebody. In the end the person that she cares for is the very person she has treated as a thing all the way along, namely the boy Tom."

Zonca's film, however, slips into many other things: arthouse longueurs, calculated overacting and borderline hysteria, not to mention some scenes that will have purer souls than mine rolling their eyes in moral outrage. For example, there's a scene in which Julia wakes up in a motel cuddling the boy she has kidnapped. It would be a tricky enough scene for any director to tackle and for any actor to perform, but as Zonca shot the scene, he realised that the boy had woken up and was staring at Swinton's breast, which had somehow become exposed. "I was like this," says Zonca, framing his face with two hands to suggest he's behind a camera, behind which are a pair of goggle eyes. "I didn't know whether this was fortuitous or terrible that her breast popped. But Tilda thought it was great. So we went with it." "And, don't forget," says Py, "the boy's mother, who was on the set at the time - she was OK with it."

Zona and Py, that diverting lunchtime double act, rise to leave. They're hoping to do some writing this afternoon. "We're writing a sex film," says Zonca. "It's set in London," chips in Py. Excellent, I say, secretly fearing it will be along the same lines as Intimacy, Patrice Chéreau's adaptation of Hanif Kureshi, which was chillingly billed as Last Tango in Lewisham. "It will be set in Notting Hill," says Zonca, pulling on his coat. "And it's going to be playful, wild, naked," he adds, gesticulating expansively as other diners stare. "We only started writing earlier this week, so anything could happen," says Py. They leave.

Last Tango in Notting Hill with lots of naked flesh, eh? Unbidden, an image of Rhys Ifans in his Y-fronts enters my head. I summon the waiter, and order that drink.

• Julia is released on December 5