French police detectives interviewed a young French writer on Monday over her claim that former IMF boss Dominique Strauss-Kahn tried to rape her in 2003, a judicial official told AFP.

Paris police have been asked by investigating magistrates to look into the writer Tristane Banon's allegation against the ex-head of the International Monetary Fund, who is also accused of sex crimes in New York.

Prosecutors will then decide whether or not to charge the 62-year-old Socialist politician with any offence.

The police are probing a complaint lodged by 32-year-old Banon that Strauss-Kahn assaulted her in a Paris flat in 2003 as she interviewed him for a book she was writing.

Strauss-Kahn, until recently seen as the favourite to win next year's French presidential elections, has dismissed the alleged Paris attack as "imaginary".

His lawyers are planning to sue Banon for defamation over the allegation, which she first made on television back in 2007.

The French probe came as the US case against Strauss-Kahn appeared to be in trouble amid doubts over his accuser's credibility.

Strauss-Kahn has been charged with sexual assault and attempted rape of a New York hotel maid on May 14, but prosecutors there have admitted to doubts over the alleged victim's testimony.