A veteran Irish-American campaigner against anti-Catholic bigotry in Northern Ireland has slammed a new Borat-style film on religion which opened in Ireland this weekend.

Fr Sean McManus, president of the Capitol Hill-based Irish National Caucus, has described Religulous, a documentary on religion by US satirist Bill Maher, as "superficial, sneering and insulting".

In the US the film has outraged Catholics who claim they are unfairly targeted by director Larry Charles, who is also behind the film Borat and TV show Curb Your Enthusiasm.

Speaking to the Sunday Tribune this weekend, Fr Sean McManus said he hoped that Religulous – its title a provocative mix of the words 'religion' and 'ridiculous' – would fail at the Irish box office.

"You would expect a documentary about religion to raise profound questions about life or death or justice and peace but this film does not. It might have a shock impact in Ireland but only for a very short time," he said.

But it's the controversial film's writer and star for whom Fr McManus reserves most of his anger.

"Even Northern Ireland has not produced worse bigots than Bill Maher and the fact that he was raised Catholic only makes his ugliness more offensive," he said.

Host of HBO's late-night talk show Real Time, Maher has described Religulous as his own personal take on religion.

It shows the comedian confronting a believer in each faith with what he sees as the apparent contradictions and idiocies of their belief systems, be it Christianity, Judaism, or Islam. These include the director of a Christian Church for "ex-gays", and an actor who plays Jesus in the "Holyland USA" theme park.

The film also ridicules the doctrine of the virgin birth of Jesus and the biblical account of the talking snake in the Garden of Eden.

"He didn't pick one normal serious, sensible, informed person to speak about their faith in God. Another part of the documentary I object to is him scoffing at 'a young Jewish woman having sex with a space God'. Well the entire Christian tradition is that Mary was a virgin. That is why she is called the Blessed Virgin Mary," said Fr McManus.