It's the sort of collapse many Americans fear, the catastrophic meltdown of institutions once considered invincible. And not even a $700bn bail-out can rescue them. At least that's if Bill Maher has his way. In a provocative new film, the Irish-American satirist takes direct aim not at the banks of Wall Street but at institutionalised religion. Maher's specific targets were once infamously described by another "born-again atheist" – commentator Gore Vidal – as "the three big anti-human religions: Christianity, Judaism and Islam".

While many people this side of the Atlantic may not yet have heard of Maher, they certainly will if and when his film is released here. His comic stock in trade is saying the unsayable, advocating truth over politeness, being unashamedly irreverent about the generally revered and offending as many upstanding citizens as possible. It's this last characteristic in which he scores most success.

The man who describes himself as a libertarian also supports the death penalty, legalised abortion and euthanasia, while describing the subject of organised religion as "the most controversial, taboo topic, ever". Hopes of even a glimmer of reverence in the film are surely dashed with the news that his cinematic collaboration is with Borat director, Larry Charles.

The film's title plays on the similarity of the words "religious" and "ridiculous" – health warning enough perhaps for those with even the most moderately pious take on life. Religulous gives form to Maher's evangelical mission in destroying credibility in the world's Big Three religions.

Unlike literary "crusades" such as Richard Dawkins's The God Delusion or Christopher Hitchens's God is not Great, Maher uses ridicule rather than reason in the film to promulgate his message that the end is nigh for belief systems with their roots in the Hebrew scriptures. Mormons and Scientologists don't get off lightly either.

A Borat-style technique induces unsuspecting believers to condemn themselves by their own words, but unlike Kazakhstan's erstwhile "reporter", Maher doesn't play the dope on screen. He utilises his varsity debating skills against believers who take the bible as literal and historical fact. Religion, he says, makes him laugh "because it's a side of a barn" in rich comedic material.

"I was raised a Catholic. But by the time I became an adult, scientific thought and rational evidence led me to believe otherwise. When I was a kid and got a cavity, I had mercury drilled into my teeth. Then, when I got older, they drilled it out – you can do the same with religion."

Some of that enlightened "drilling" may have been from his time as an Ivy League student at Cornell, where he studied English and history, graduating in 1978. A year later Maher began establishing his career as a stand-up comic in New York, quickly followed by appearances on the Johnny Carson and David Letterman shows. Some minor film roles followed, as well as script-writing on the sitcom Roseanne.

But his reputation for prompting political debate and controversy through his comedy projected Maher into the limelight as host of a chat show called – what else? – Politically Incorrect. Extracts from his HBO show, Real Time with Bill Maher, were turned into a book called New Rules. In one section he directs his acerbic wit to interpretations of freedom – as defined by Kris Kristofferson.

"'Freedom's just another word for nothing left to lose', apparently, without considering that 'nothing left to lose' is actually four words. In doing so, Kris Kristofferson followed the rules of neither math nor grammar – what a loser."

Maher's signature delivery is one of bored exasperation, particularly when talking of his current pet hate – vice-presidential candidate Sarah Palin. He describes Levi Johnston as "America's number one political prisoner." Those up to speed on the presidential campaign will know Johnston is the father of 17-year-old Bristol Palin's baby. Maher set up a spoof website to raise funds enabling Johnston to "buy his freedom".

While his satirical rants take no prisoners, Maher has come clean on some occasions where he overstepped the mark. He was unrepentant when his contract with the ABC network was withdrawn in September 2001 after he agreed with a commentator on air that "the 9/11 terrorists were not cowards. We have been the cowards lobbing cruise missiles from 2,000 miles away."

But it was after comparing dogs to "retarded" children on a Politically Incorrect show, when he unequivocally apologised. "I was wrong. What I said was hurtful to people. And I feel terrible about it."

His comic strength as a social and political commentator lies in the ability to turn stereotypical attitudes on their head. Just last week, Maher "pleaded" with viewers not to reject John McCain "just because he's white. The recent news from Wall Street has made us all less tolerant and only reinforces the stereotype that white people are shiftless, thieving, welfare queens," he intoned, before showing shots of the four men who head up Fannie Mae, Freddie Mac, Lehmann Brothers and AIG who, "all happen to be white, and responsible for stealing. But they are just a product of the neighbourhood they grew up in, and the schools where they learnt to steal – like Harvard and Yale."

It's religion, rather than white, corporate America, that offers the richest comedic seam for Maher now: "Not even George Bush provides such good material," he says. So far, it has been the Catholic church in the US that feels most targeted by Religulous – the film from a former Catholic who equates any form of religious belief with extremism.

With the debate set to intensify generally as to where free speech should end and self-censorship
begin – especially in regard to religious sensibilities – it's left to the new wave of comics such as Maher to explore that sensitive divide. If the stand-up himself is not struck down first, that is.