Critics panned The Da Vinci Code on Wednesday ahead of the world premiere of the year's most eagerly awaited movie.

Opening the annual Cannes film festival, Ron Howard's adaptation of the Dan Brown bestseller was described variously as 'grim', 'unwieldy' and 'plodding'.

Even before its general release on May 18 and 19, the movie starring Tom Hanks generated much controversy as Christians around the world called for it to be banned.

The novel has enraged religious groups because one of its characters argues that Jesus Christ married Mary Magdalene and had a child by her, and that elements within the Catholic Church resorted to murder to hide the truth.

In Thailand on Wednesday, a police-run censorship board overturned an earlier decision to cut the last 10 minutes of the film, but insisted the distributor added disclaimers stating it was fiction.

And in addition to Vatican calls to boycott the picture, the Indian government said it would show the movie to Christian groups before clearing it for release. In the mainly Catholic Philippines the censors have given it an 'adult only' rating.

At a news conference, Howard and Hanks defended the film, calling it a piece of fiction. British actor Alfred Molina, who plays a Machiavellian bishop in the movie, blamed the media for creating controversy where there was little or none.

At a screening late on Tuesday in Cannes, members of the audience laughed at the thriller's pivotal moment, and the end of the $125 million picture was greeted with stony silence.

Trade publication Variety had barely a nice word to say.

"A pulpy page-turner in its original incarnation as a huge international bestseller has become a stodgy, grim thing in the exceedingly literal-minded film version of The Da Vinci Code," wrote Todd McCarthy.

Lee Marshall of Screen International agreed.

"I haven't read the book, but I just thought there was a ridiculous amount of exposition. I thought it was plodding and there was a complete lack of chemistry between Audrey Tautou and Tom Hanks," he said.

While critics argue the controversy surrounding the film, and the fact that more than 40 million people have bought the book, will ensure a strong box office performance, word-of-mouth is likely to hit sales later on.

The movie industry will be watching The Da Vinci Code particularly closely after the first two summer blockbusters--Mission: Impossible III and Poseidon -- failed to find the Hollywood Grail of box office success.

Hanks defended the film against its critics.

"This is not a documentary. This is not something that is pulled up and says 'These are the facts and this is exactly what happened.' People who think things are true might be more dangerous than people who ponder the possibilities that maybe they are and maybe they aren't," he said.

Howard had some advice for those who objected to the story.

"There's no question that the film is likely to be upsetting to some people. My advice is to not go and see the movie if you think you're going to be upset," he said.

Ian McKellen, an openly gay actor who plays Leigh Teabing in The Da Vinci Code, sought to make light of the controversy.

"I'm very happy to believe that Jesus was married. I know the Catholic Church has problems with gay people and I thought this would be absolute proof that Jesus was not gay," he said.

The Da Vinci Code premiere late on Wednesday kicks off 12 hectic days of screenings, interviews, photocalls and partying in Cannes, the world's biggest film festival.