A lesbian love movie that scooped best film at Cannes opens next week, but its Palme d'Or has been tarnished by a row between the director and his stars over the filming of its graphic sex scenes.

The three-hour-long "Blue is the Warmest Colour" caused a sensation at this year's Cannes film festival, making stars out of its two lead actresses, Adele Exarchopoulos and Lea Seydoux.

The pair were all smiles on the French Riviera as they posed for photographs with the film's French-Tunisian director, Abdellatif Kechiche.

Chairman of the jury Steven Spielberg hailed it as a "profound love story", adding that the judges had been "absolutely spellbound" by the brilliance of the women's performances and "the way the director... let the characters breathe".

But fast forward several months and the mood surrounding the film has soured, with bitter complaints from both actresses about Kechiche's working methods.

In an interview published on September 1 by US website The Daily Beast, Exarchopoulos said that she had been unprepared for the extent to which Kechiche required her to immerse herself in the role.

"Once we were on the shoot, I realised that he really wanted us to give him everything. Most people don't even dare to ask the things that he did, and they're more respectful," she said.

Seydoux complained that a 10-minute sex scene in the film took a full "10 days to shoot".

And both women complained about a fight scene.

"It was horrible. She (Seydoux) was hitting me so many times and (Kechiche) was screaming 'Hit her! Hit her again!'," Exarchopoulos said.

With the film due for release in France next week, the pair again aired their complaints, with Seydoux telling TV magazine Telerama that filming was "horrible" and that she did not think the film should be released.

'He loves his actresses to let go'

"For me, this film should not come out, it has been sullied too much. The Palme d'Or was only a brief moment of happiness, afterward I felt humiliated and dishonoured, I felt a rejection of my person, (and) that I live like a curse," she said.

Exarchopoulos, meanwhile, told French television that Kechiche was a "tortured genius" but that his demands had harmed both of them.

"He made us ill psychologically at times because he loves his actresses to let go and it's hard to do," she said.

For his part, Kechiche has responded by saying he believes the comments show "a lack of respect for a metier that I regard as sacred".

And French actress Hafsia Herzi, who has worked with Kechiche, launched a defence of the director.

He is a "very humane man who gives a chance to people even when they don't have experience", Herzi said in French film magazine So Film.

Critic and film historian Jean-Michel Frodon said Kechiche's film would join the ranks of movies that have seen well-publicised difficulties between directors and their stars.

Such tensions often came about when actors felt they were giving things to the camera "having exhausted their defences or self-control", he said.

Cannes film festival artistic director Thierry Fremaux, meanwhile, recalled that when "The Shining" came out audiences were unaware of the on-set problems between Jack Nicholson and Stanley Kubrick.

"Jack Nicholson today, like Malcolm McDowell in (Kubrick's) 'A Clockwork Orange', says that shooting was awful but that they are grateful to Kubrick for everything that the films brought them," he said.

"Blue is the Warmest Colour" opens in France and Belgium on October 9, followed by other European countries between October 10 and 25.

It will have a limited release in the United States from October 25, as well as slots at four film festivals this month, including Chicago and New York.