US prosecutors have asked a judge to dismiss all criminal charges against Dominique Strauss-Kahn, the former International Monetary Fund chief accused of sexual assaulting a hotel maid.

"The nature and number of the complainant's falsehoods leave us unable to credit her version of events beyond a reasonable doubt, whatever the truth may be about the encounter between the complainant and the defendant," the office of Manhattan District Attorney Cyrus Vance jnr said in a filing today.

"If we do not believe her beyond a reasonable doubt, we cannot ask a jury to do so."

Mr Strauss-Kahn, 62, was arrested in May after Nafissatou Diallo told police he attacked her when she came to clean his suite at the Sofitel in midtown Manhattan, New York. He pleaded not guilty to the charges.