LILLE, France – French police detained former IMF chief Dominique Strauss-Kahn for questioning Tuesday over allegations he took part in orgies in Paris and Washington with prostitutes paid for by businessmen.

The 62-year-old former Socialist minister, who until last year was the frontrunner to replace Nicolas Sarkozy as president of France, had been summoned as a witness but prosecutors said he was now a suspect.

He turned up voluntarily at a police station in the northern city of Lille and prosecutors said he would be detained on suspicion of “abetting aggravated pimping by an organised gang” and “misuse of company funds”.

A magistrate will decide whether the evidence supports charges on these or other potential offences. He could be cleared, be charged and released on bail or remanded in custody pending an eventual trial.

Under French law, aggravated organised pimping carries a prison term of up to 20 years and profiting from embezzlement five years and a large fine.

Between interrogations, the millionaire international statesman was to be held in a spartan 7.5-square-metre (80-square-foot) cell with a simple foam mattress, a sink and a hole-in-the-floor squat toilet.

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

They will also seek to determine whether Strauss-Kahn knew that the escorts were paid with funds fraudulently obtained by his hosts from a French public works company, for which one of them worked as a senior executive.

Paying a prostitute is not illegal in France, but profiting from vice or embezzling company funds to pay for sex can lead to charges.

The former managing director of the International Monetary Fund admits he has an uninhibited sex life, but denies any role in pimping or corruption and has indicated he will deny any criminal wrongdoing.

Lawyer Henri Leclerc has said his client may not have known he was with prostitutes as “in these parties, you’re not necessarily dressed. I defy you to tell the difference between a nude prostitute and a nude woman of quality.”

Two businessmen, Fabrice Paszkowski, a medical equipment tycoon with ties to Strauss-Kahn’s Socialist Party, and David Roquet, former director of a local subsidiary of building giant BTP Eiffage, have been charged.

The pair have alleged links to a network of French and Belgian prostitutes centred on the Carlton Hotel in Lille, a well-known meeting place of the local business and political elite in a city run by the Socialist Party.

In all, eight people have been charged in connection with the “Carlton affair” — including three executives from the luxury hotel itself, a leading lawyer and the local deputy police chief, Jean-Christophe Lagarde.

The last of the sex parties is said to have taken place during a trip to Washington and the IMF headquarters between May 11 and 13 last year by Paszkowski and Roquet, in part to discuss Strauss-Kahn’s presidential bid.

One day later, on May 14, Strauss-Kahn’s career fell apart when he was arrested in New York following allegations that he had subjected chambermaid Nafissatou Diallo to a brutal sexual assault in his hotel suite.

The case against him eventually collapsed when prosecutors began to doubt Diallo’s credibility as a witness, and Strauss-Kahn returned home to France to face further investigation and scandal.

First, 32-year-old French writer Tristane Banon accused him of attempting to rape her in 2003. Prosecutors decided there was prima facie evidence of a sexual assault, but ruled that the statute of limitations had passed.

Then, Strauss-Kahn was linked to the Carlton case when suspected escorts gave his name to police probing a vice ring linked to notorious pimp Dominique Alderweireld, known in the underworld as “Dodo la Saumure”.

Strauss-Kahn’s multi-millionaire heiress wife, journalist Anne Sinclair, has stood by him since the allegations erupted, but the website she edits — the French edition of the Huffington Post — led its front page with the scandal.

She made no editorial comment, but her team reported the case in depth.

Few in France doubt that, but for the sex scandals, it would have been Strauss-Kahn and not Francois Hollande running against Sarkozy in April’s presidential election, and the incumbent’s camp was quick to seek advantage.

“Perhaps, at the end of Dominique Strauss-Kahn’s interrogation, we will hear useful and interesting news about the behaviour of Socialist Party branches in the north,” said Sarkozy’s campaign spokeswoman Nathalie Kosciusko-Morizet.

“If Francois Hollande is where he is today, it is because Dominique Strauss-Kahn is where he is today,” she added.

The involvement of businessmen and police officers raised suspicions they intended to curry favour with a presidential contender by procuring women for him, but they are reported to have denied this during questioning.