Former IMF chief Dominique Strauss-Kahn was questioned by French police for a second day today over allegations that he took part in sex parties organised by a corrupt vice ring.

The 62-year-old former Socialist minister, who until last year was the frontrunner to replace Nicolas Sarkozy as president of France, was taken into custody on Tuesday in the northern city of Lille.

He was questioned all day then magistrates prolonged his detention for 24 hours. The interrogation could be extended again, but sources close to the investigation said he was expected to leave custody later today.

A magistrate will have to decide whether he is released without charge or placed under formal investigation on charges of "abetting aggravated pimping by an organised gang" and "misuse of company funds."

If charged, he could be released on bail or remanded in custody pending a trial. Under French law, aggravated organised pimping carries a prison term of up to 20 years and profiting from embezzlement five years and a fine.

The wealthy international statesman, whose wife is an heiress and who normally lives at one of Paris most exclusive addresses, was held overnight in a spartan 7.5-square-metre cell with a squat toilet.

Investigating magistrates want to know whether he was aware that women who entertained him at parties in restaurants, hotels and swingers' clubs in Paris and Washington were paid prostitutes.