Cannes jury head Quentin Tarantino has said Michael Moore's Fahrenheit 9/11 won the Palme d'Or on merit alone.
Michael Moore shows off his prize at Cannes
The documentary alleges links between US President George Bush and top Saudi families, including the Bin Ladens.
But Kill Bill director Tarantino insisted Moore's overt political themes did not influence his jury's choice.
"I knew all this politics crap would be brought up," he said. "We all agreed that Fahrenheit 9/11 was the best movie of the competition."
Tarantino said when he was on stage with Moore on Saturday night to present the award, he told the director politics had nothing to do with the choice.
"I just whispered in his ear and said, 'I just want you to know it was not because of the politics that you won this award, you won it because we thought it was the best film that we saw.'"
Tarantino denied the film's choice was a political decision
Moore has made no secret of his wish that the film will turn US voters against Mr Bush in this autumn's presidential election.
It was the first documentary to win the top prize since Jacques Cousteau's The Silent World in 1956.
The film uses Moore's customary satirical style to accuse Mr Bush of stealing the presidential election in 2000, ignoring terrorism warnings before 11 September 2001 and fuelling fears of more attacks to secure Americans' support for the war in Iraq.
While produced by Miramax, the studio's parent company Disney has refused to distribute it and Moore is now looking for a third party to get the film into US cinemas.
But Moore told the Associated Press news agency he was hopeful of striking a deal soon.
"I would be surprised within the next 24 hours if we don't have somebody," he said.
"Miramax has been fielding calls all day."
For the first time in the festival's history, Cannes' jury members were able to talk about their choices at a press conference on Sunday.
The Cannes jury lined up to discuss their choices
US actress Kathleen Turner said of Fahrenheit 9/11: "We felt this was more than a documentary."
Tarantino said he had encountered some of the best film criticism he had ever heard, and joked about taking his jurors on tour.
"Have jury, will travel," he said.
British actress Tilda Swinton denied she had clashed with Tarantino. The two had disagreed over the state of the UK's film industry at the event's opening press conference.
"Quentin Tarantino has got an enormous mouth," she said, adding to laughter: "But he's got two enormous ears."