A French incest "fairytale" brought a touch of scandal to the Cannes Film Festival Tuesday but even the frisson of illicit sex couldn't save the movie from a critical mauling.

"Marguerite and Julien", one of five French movies among the 19 contenders for the top prize at the world's biggest cinema showcase, tells the true story of aristocratic siblings in 16th century France whose deep love turns into physical passion when they reach adolescence.

French actress-turned-director Valerie Donzelli said she was attracted to the bohemian spirit of the story, adapted from an unrealised screenplay by Jean Gruault, who wrote it in the 1970s for French New Wave icon Francois Truffaut.

Flouting religion, the law and their family, the star-crossed lovers run away together from the chateau of their childhood, and Marguerite quickly gets pregnant.

But the authorities soon catch up with them with arrest warrants for a capital crime. When their father appeals to the king's secretary of state for clemency, he refuses on image grounds: "All of Europe says the French court is a whorehouse."   
Donzelli tells the once-upon-a-time story with a childlike innocence, narrated by latter-day girls in an orphanage breathlessly telling the scandalous tale.

"The idea was to depict Marguerite and Julien like a myth or a legend -- they were like rock stars who fascinated these orphans," she said.

"The film needed to be dealt with in that manner so we had the idea of telling the fairytale to these young children."

Donzelli also weaves in anachronistic elements such as police helicopters, electronics and blaring pop music -- reminiscent of Sofia Coppola's "Marie Antoinette", which was also panned by Cannes critics when it opened the festival in 2006.

However the reaction to "Marguerite and Julien" has proved far more vicious.

- 'Buttock-clenchingly embarrassing' -

Film industry bible Variety remarked drolly that "incest has never felt so cloying".

"The film is a painfully silly, laughably naive Romance with a capital 'R'," reviewer Jay Weissberg said.

Reviewer Peter Bradshaw of London's The Guardian newspaper said the movie "joins the ranks of Cannes' most appallingly bad films", calling it "buttock-clenchingly embarrassing".

"There are turkeys and there are turkeys. This is a turkey de luxe, with stuffing, bread sauce, and a paper hat," he said.
"It is strange that Cannes will keep on mystifyingly offering us terrible movies from its home turf or home team."

Trade magazine The Hollywood Reporter called it "bonkers" in style and "rather odd" that the sex between siblings was not presented as "problematic in any way", even when told as a children's story.

"Only in France," it concluded.

French newspaper L'Express admitted the film was likely to divide critics but hailed "the uniqueness of (Donzelli's) vision and tone -- never affected but ceaselessly inventive".

Most of the French films in competition this year have drawn only mixed reviews.

However the biggest competition flop at the festival so far has been the US movie "The Sea of Trees", a far-fetched existential drama directed by Gus Van Sant and starring Matthew McConaughey and Naomi Watts. It was loudly booed at its press previews.

Cannes tends to revel in scandal and has another sure-fire provocation in the offing later this week.  

Gaspar Noe, an Argentinian-born director who works in France will be showing his movie "Love" -- suggested to be heavily pornographic, based on an X-rated poster he released online -- in a midnight screening.

The festival wraps up Sunday with a gala awards ceremony where a jury led by US filmmakers Joel and Ethan Coen will decide the Cannes prizes.