Larry Charles is turning his razor-sharp wit on world religion - and no one will be spared

If you ever wondered who dreamed up Cosmo Kramer, the hipster doofus with a mistrust of authority at the centre of one of American television's most successful comedies, Seinfeld, then look no further than Larry Charles, a Jewish-American comedian with an encyclopedic brain and ZZ Top beard.

Charles bestrides the upper echelons of the US comic fraternity, cutting his teeth as a staff writer on Seinfeld before joining the equally colossal Larry David to direct Curb Your Enthusiasm, about to launch into its seventh series. With the direction of Sacha Baron-Cohen's Borat film in 2006 under his belt, Charles has now confirmed his ascendancy into the joke-makers' A-list. Everything he touches immediately morphs into a metallic clutch of Emmies or Golden Globes.

The 52-year-old funny man is set to appear at London's BRITDOC festival, kicking off on Wednesday. He is down to talk about Religulous – a documentary about religion crafted with fellow veteran US comic Bill Maher – its title a fusion between the words "religion" and "ridiculous". The movie sees Maher travelling to numerous religious destinations, including Jerusalem and the Vatican, to interview a raft of outlandish zealots, including "Jews for Jesus", polygamists and Satanists. Its release is scheduled for the US in October, with other countries to follow.

"This has been a subject that I have been interested in since I was a child. Since then, it has variously consumed and obsessed me. As it turned out, Bill was obsessed by the same subject," he explains. "My grandfather went to temple every day and was a very pious man. Me, after my bar mitzvah, I was done with it. My father taught me how to be a jokester about it all, though. He would sit there during Passover and make jokes and puns with Hebrew words."

Jewishness is central to his comedy and his worldview. "You can't dismiss any seminal influence. I grew up in Brighton Beach, New York, where essentially everyone is Jewish. I grew up thinking the whole world was like that. Obviously, Jewishness gives you a historical background, and a comedic one. The movie moguls who started the movie business tried to create an idealised gentile world. The idea of a white picket fence world is a Jewish creation. So it's pervading American culture and I know it has had an impact on me and my work."

He is not the first comedian to take on religion. Does he not feel that religion is an easy target? "It is," he says. "Everybody knows a joke about a priest or a rabbi, and it is good to incorporate an irreverent take on that. But at the same time it is very complex, it is very intricate, and is a moving target. But there are very few examples of people using it in a commercial medium. I am surprised no one has done it before, apart from maybe the Pythons. And, like them, I want to offend everybody. I don't just want to offend one group. In that sense I am not discriminating against anybody."

He knew that he and Maher, who share a similar background, would get along easily. "In fact, up until we worked on this project, the pair of us had undergone parallel lives without meeting each other," he says. We'd even slept with the same women.

"Then when the project came around it was easy for us to get along. We got the money together quickly and started shooting quickly. No notes or meetings."

For Religulous, Charles brought his knowledge of improvisation, something that he incorporated forcefully into his direction of Borat. "Bill had written an outline as had I. And then I synthesised the two. We planned the shoot based on that. I am a believer in not trying to impose too much before shooting takes place. You need to let the process happen. Let that be the movie. Although I had in the back of my mind a sense of structure and tone which I wanted to include. "I was able to bring that to Borat. Sacha [Baron-Cohen] has this push and pull tension and dichotomy between control and anarchy. I like that tension, it is good for film-making. It makes for more spontaneity. It makes film-making more urgent and real. I learned that from [Jean-Luc] Godard or [Werner] Herzog or Michael Moore doing a very non-Hollywood, non-corporate, very handmade form of movie-making."

He adds that YouTube has brought a new dimension to his work. "I am an encyclopedia freak and YouTube is like an encyclopedia of video. It excites me that on a whim you can type anything in and there's a film about it on there. It is amazing to me. I am of an age where computers are not second nature. But it has confirmed my belief in making films handmade and taking them direct to the consumer."

Charles says other projects he has in the pipeline are too secretive to discuss. He denies that he is directing a new National Lampoon movie, as has been rumoured, and confirms that a recent collaboration with rapper Kanye West for HBO was canned by the network after a pilot was shot. He does, however, say that since being introduced to British comedy in detail by Baron-Cohen, he has become a massive fan. "I think it's amazing and singular and a lot of people [Steve Coogan and Ricky Gervais, among others] have been drafted over here. What is great is that stuff from an iconoclastic point of view is given a forum. This is much harder in the US where television is more mainstream. Here, it's harder to produce little jewels. In the UK, it's not about economics, it's about creativity. In terms of Little Britain [broadcast on HBO in September] what I find interesting is being able to juxtapose scatological humour with serious satire, and I think those two things can co-exist. I am always looking for that."

BRITDOC is running from 23-25 July at Keble College, Oxford. For more information see www.britdoc.org