LILLE (AFP) - A French court on Friday acquitted former International Monetary Fund (IMF) chief Dominique Strauss-Kahn of pimping charges, drawing a line under the latest in a series of legal woes over his sexual escapades.

The 66-year-old economist merely nodded his head in acknowledgement of the verdict, the finale of a colourful trial which dragged intimate details of his sex life into the public eye.

His acquittal on the charge of "aggravated pimping" did not come as a surprise after the prosecutor called for him to be let off due to lack of evidence at the end of a three-week trial in February.

The trial was the latest in a long series of high-profile court cases in the past 15 years in which Strauss-Kahn has landed in the dock for corruption or sexual scandals that have fizzled out.

Strauss-Kahn saw his high-flying career at the head of the IMF - and his French presidential prospects - implode when a New York hotel maid accused him of sexual assault in 2011.

Not long after those criminal charges were dropped and the case settled in a civil suit, his name cropped up in a probe into a prostitution ring in northern France, which provided sex workers for orgies he attended.

He was charged with aiding and abetting the prostitution of seven women - a charge punishable by up to 10 years in prison.

The courtroom in the northern city of Lille heard lurid details of champagne-fuelled orgies attended by Strauss-Kahn as his lawyers accused the court of putting his morals, and prostitution itself, on trial.

Strauss-Kahn said that while he was a libertine who enjoyed group sex, he was unaware any of the women attending soirees in Paris, Brussels and Washington, had been paid to be there.

Former prostitutes gave dramatic testimony about nights of "carnage", saying Strauss-Kahn would have been "naive" to be unaware of their role and recounted brutal scenes in which he sodomised them.

Their lawyers' insistence on Strauss-Kahn's preference for anal sex caused the otherwise unflappable man to lose his patience, saying he was not on trial for "deviant practices".

"I must have a sexuality which, compared to average men, is more rough. Women have the right not to like that, whether they are prostitutes or not," he said.

He said the use of prostitutes "horrified" him and that paying for sex would be too great a risk for a man at the head of the IMF, which was busy "saving the world" from the financial crisis that began in 2008.

In their closing arguments, his lawyers said the case against him had "collapsed" into nothing more than an indictment of Strauss-Kahn's morals, and the prosecution appeared to agree.

Main prosecutor Frederic Fevre called for Strauss-Kahn to be acquitted, saying that "neither the judicial enquiry nor the hearing have established that Mr Strauss-Kahn is guilty." In another boost for Strauss-Kahn, the two former prostitutes who testified dropped a civil lawsuit against him, with their lawyers conceding they lacked enough proof to win the case.

Strauss-Kahn found himself in the dock alongside a colourful cast of 13 characters accused of taking part in a prostitution ring in northern France.

Seven of them, including brothel owner Dominique Alderweireld, known as "Dodo the Pimp", were also acquitted.

The former manager of the upmarket Carlton hotel in Lille, where some of the accused threw sex parties for well-connected local businessmen and police officers attended by prostitutes, was given a one-year suspended sentence.

It is unclear what the acquittal means for the former star in the Socialist party, but a poll before the trial showed 56 per cent of French people questioned had no desire to see him return to politics and saw him as immoral and a misogynist.

However, 79 per cent of people questioned thought Strauss-Kahn would have been a better president than the deeply unpopular Francois Hollande.