He's been given a kicking at the local elections and was last night facing a bloody nose at the European polls. So it's just the kind of cheerful news Tony Blair needs now: that the cinematic equivalent of a rottweiler, Michael Moore, is contemplating making the prime minister his next victim.

Fresh from savaging President George Bush in the critically acclaimed Fahrenheit 9/11, the filmmaker is now thinking about making a movie about Mr Blair and Britain's role in the war on Iraq.

"I personally hold Blair more responsible for this war than I do George Bush. The reason is, Blair knows better," Moore said in an interview with the Reuters news agency. "Blair is not an idiot. What is he doing hanging around this guy?"

America has been bracing itself for the release of Fahrenheit 9/11, which won the Palme d'Or at the Cannes film festival. There has even been speculation that the film could help to tip the November US presidential election in favour of Mr Bush's rival, John Kerry.

The documentary, which condemns US involvement in Iraq and explores the alleged links between the Bush family and powerful Saudi Arabians, including Osama bin Laden's family, is considered so incendiary that its production company, Disney, blocked its subsidiary Miramax from releasing it in the US. Miramax chiefs Bob and Harvey Weinstein recently bought back the film from Disney and will release it on June 26.

Moore, described as a "slimeball" by George Bush senior for his denunciation of the Bush dynasty, said it had been a difficult decision to leave Tony Blair out of his current film. But he said he now wanted to take a closer look at the British leader's role in backing the war in Iraq and sending troops into harm's way.

"What I decided is that I need to make a separate film about Blair, at some point here. I need to do something about Blair and Britain," he said.

Moore said Mr Blair was like the US president's older sibling and should be asked how he could have let him get into such trouble.

He said he was steeling himself for efforts by Bush supporters to discredit Fahrenheit 9/11. He has hired two former political advisers to Bill Clinton to establish a "war room" that will immediately support any claims made in the movie that come under attack.

"You come at me with anything, we come back with the truth," he said.