French prosecutors say they are dropping an investigation into whether former IMF chief Dominique Strauss-Kahn took part in a gang rape alleged to have taken place in the United States.

The woman who made the complaint has retracted her evidence, the prosecutors said on Tuesday.

However Strauss-Kahn, 63, is still under investigation with three other men over their alleged roles in a prostitution ring. Strauss-Kahn denies the allegations.

The Belgian woman who was allegedly raped wrote to French police in August to say she had consented to sex acts and was not pressing any charges, the prosecutor's office in Lille said.

It added in a statement that a preliminary investigation was being shelved as no offence had been committed.

Strauss-Kahn, two businessmen and a police chief were charged in March with "aggravated pimping in an organised gang" for allegedly contributing to the procurement of prostitutes for sex parties.

The former politician admits attending sex parties in France and the US but claims he did not know the women involved were being paid to take part.

The pimping investigation is ongoing with another hearing due at the end of November but Strauss-Kahn's lawyer, Henri Leclerc, said he was confident his client would ultimately be cleared of any wrongdoing.

'No pimping'

"There is no hint he was involved in pimping. You will see that emerge although right now this is fuelling scandal."

Strauss-Kahn's career collapsed spectacularly after his arrest last year on accusations that he sexually assaulted a New York hotel maid.

The alleged victim in that case, Nafissatou Diallo, is now pursuing Strauss-Kahn in a civil lawsuit in the US,
alleging sexual assault.

Earlier this year Strauss-Kahn also separated from his wife of some 21 years, Anne Sinclair.

His reputation was further shredded on his return to France as details of another alleged attack and the pimping case surfaced.

The case, known as the "Carlton affair" in France, centres around allegations that business leaders and police officials in Lille operated a vice ring supplying girls for sex parties, some of which are said to have taken place at the Carlton Hotel.

Source: Agencies