Conservative activists in the U.S. are attacking the Michael Moore film Fahrenheit 9/11 on both the regulatory and commercial fronts.

The group Citizens United wants the U.S. Federal Election Commission to rule that ads for the movie, which are highly critical of U.S. President George Bush, are deemed illegal.

They claim the ads should fall under U.S. federal campaign finance laws, which prohibit the use of corporate money to identify a presidential candidate more than 30 days before his party's nominating deadline.

Bush features prominently in the film's ads. He will formally be nominated by the Republican Party at a convention in New York City that starts Aug. 30.

Moore terms the effort "a blatant attempt on the part of a right-wing, Republican-sponsored group to stop people from seeing my movie."

"It's a violation of my First Amendment rights that I cannot advertise my movie. It's a movie," Moore says, adding he is politically independent.

The general counsel of the Federal Election Commission has recommended that Moore be barred from airing radio or television ads for the movie after July 30.

While Moore thinks his film should qualify for a media exemption, Citizens United argues it is propaganda and doesn't qualify.

Because Lions Gate Entertainment Corp. is a Canadian company, the ads should also be subject to a ban on the use of foreign money for ads identifying presidential candidates close to elections, the group says.

Moore -- who won an Academy Award for Bowling for Columbine, a look at America's gun culture -- has been clear about the effect he'd like to see his latest film have: He wants voters to toss Bush out of office on Nov. 2.

"I'm preaching to two choirs: the left, and the left out," he told reporters in Washington, where the film was previewed Wednesday night. "The choir of the left-out, that 50 per cent that doesn't vote, if I can convince just a few of them to come back in and participate in this great democracy, I think that'll be a good thing come Nov. 2."

The film won the Palme d'Or at this spring's prestigious Cannes Film Festival.

It shows clips like Bush urging nations to "do everything they can to stop these terrorist killers" -- just before hitting a golf ball.

In another clip, Bush said if he hit every shot well, "people'd think I wasn't working."

Fahrenheit 9/11 also examines the relationship between the Bush and bin Laden families, takes on the anti-terrorist Patriot Act and provides a graphic look at the Iraq conflict.

Conservative groups, who don't like Moore in any event, have been attacking the film.

"My stomach churned as I read accounts of how hundreds of members of the press cheered wildly at the press screening of Michael Moore's venomous anti-Bush movie, Fahrenheit 9/11. Whose values do the members of the news media and the Hollywood crowd most relate to?" wrote Howard Kaloogian, chairman of Move America Forward, on the group's website.

The group -- described by Moore as a "fake grassroots front group" created by a Republican public relations firm -- has been urging theatres not to show it, apparently with some effect.

While it was supposed to open in 1,000 theatres in the U.S. on June 25 (it opened Wednesday in New York), that has fallen to 500.

Moore lost an effort to have the film's rating reduced to PG-13 from R. Canadians under the age of 14 can see the movie with a parent or guardian.

The film was produced by Miramax, a formerly independent company now owned by Disney.

In May, Disney announced it wouldn't let Miramax distribute the film in the U.S. That dispute was eventually resolved.