A darker side of female sexuality was on display in Cannes in a film portraying a woman who seduced a schoolboy and built a picture-perfect life with him after a tabloid scandal.

Starring Julianne Moore and Natalie Portman, "May December" takes the viewer on a rollercoaster of moral ambiguity as it looks at the couple living a life of apparent suburban bliss with their children despite being on the sex offenders register.

Portman plays an actor who spends time with the family as she prepares to play the woman at the heart of the scandal, played by Moore.

Her arrival opens up buried wounds, and Portman's character makes questionable decisions. 

The 41-year-old star told AFP she loved to see the women "behave in morally ambiguous ways".

"The entire range of human behaviour should be accessible to women because women are simply humans," Portman said.

"It always drives me crazy when people are like, oh, if only women rule the world, it would be a kinder place. No, women are humans and come in all different complexities."

Reviews were largely positive, with IndieWire enjoying the "deliciously campy drama" and The Telegraph calling it a "thrilling psychological tennis-game". 

"May December" became an immediate contender for an award on the final night at Cannes next Saturday. 

Many felt director Todd Haynes was robbed in 2015 when his landmark lesbian romance "Carol" starring Cate Blanchett and Rooney Mara failed to take home the Palme d'Or (though Mara took an acting prize). 

Haynes said he missed the days when films had an easier time "asking questions and debating the morality".

It is getting "harder and harder to make those kinds of films", he told AFP, with society no longer "comfortable with being uncomfortable. I think that's the death of thinking, the death of social critique and criticism."

- Repressed desires -

Portman shot to stardom at age 12 in "Leon", a film by French director Luc Besson which led her to be sexualised as a child, and towards which she has said she now has complicated feelings.

The film was inspired by Besson's relationship with French actress and director Maiwenn, who he married at 16. Maiwenn starred in and directed "Jeanne du Barry", alongside Johnny Depp, which caused a scandal as it opened at Cannes this year.

Besson, who directed "The Fifth Element", has faced several rape allegations, which Portman said she found "devastating", without wanting to give more details.

"May December" is among several films at Cannes this year taking a deeper dive into the inner lives of women.

"I think that there is no limit to how much it can be explored, so I'd like to see more," said Portman.

Haynes said the movie explored our refusal to look at ourselves honestly.

"We repress a lot of our desires for the best reasons. A civilised society exists by holding back." 

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