* Strauss-Kahn was at 2-3 sex parties a year -lawyer
* "Offense of lust" is nothing illegal - lawyer
By Alexandria Sage
PARIS, March 27 (Reuters) - Lawyers for disgraced former IMF boss Dominique Strauss-Kahn said on Tuesday he was being hounded for his "libertine ways" and that they would challenge a judicial inquiry where he is suspected of participating in pimping in France.
Strauss-Kahn's French lawyers hit back after an overnight announcement that he had been formally put under investigation in a prostitution scandal in the northern city of Lille, on counts that could expose their client to up to 20 years in jail.
"We are convinced a great injustice has been committed," said Strauss-Kahn's lawyer, Henri Leclerc.
Investigators are looking into whether the 62-year-old was aware he was dealing with prostitutes and pimps when attending sex parties in Lille, Paris and Washington in 2010 and 2011 that were organised by business acquaintances in the region.
Leclerc said Strauss-Kahn - a former finance minister and globe-trotting head of the International Monetary Fund - had participated in two or three "libertine gatherings" a year over five years, "with friends, and women who were friends of his friends."
Even if Strauss-Kahn, who is married to the popular journalist Anne Sinclair, knew the women were prostitutes, it would not be illegal in France to pay for their services.
However, magistrates are investigating whether he participated in "complicity in a pimping operation." Such accusations were "nauseating," said Leclerc.
"Everyone can say whatever they want about the moral side of it. But that doesn't mean it's forbidden anywhere in the penal code," he said.
"In reality, what he's being pursued for here is something like an offense of lust. What he's being blamed for is his libertine ways."
Eight people have already been arrested in the case, and a construction firm Eiffage fired an executive suspected of using company funds to hire sex workers.
Prior to the hearings that led to him being officially placed under inquiry on Monday night, he said he was victim of a media lynching in a country where the press traditionally draws an almost indelible line between public and private life.
Strauss-Kahn's latest problems come in a week when the man once tipped to become France's next president is back under fire in New York, too. Hearings in a civil case brought by a woman who accused him of trying to rape her in a Sofitel hotel suite last May begin on Wednesday.
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Leclerc characterized the case against Strauss-Kahn as a moral witchhunt that exceed the bounds of the law.
Moreover, he said, the individual liberties of citizens were threatened in the case, and considerable sums and months of police work were wasted "to try to penetrate the private life of Dominique Strauss-Kahn."
Strauss-Kahn was ordered to pay bail of 100,000 euros ($133,300), and forbidden to contact witnesses, the press, and others involved in the case. Leclerc said he would appeal those conditions and also seek to have the investigation thrown out.
Text messages sent by Strauss-Kahn to his friends could be the crux of the legal case, a source close to the investigation told Reuters.
Those messages, which referred to upcoming soirees and the women who would be there, might be interpreted as meeting the threshold of complicity in pandering, the source said.
Under French law, that legal definition is: "helping, assisting, or protecting prostitution, taking profit from prostitution ... hiring, training or leading someone towards prostitution."
Opening an official investigation usually, but not always, leads to charges being filed and a trial taking place.
U.S. PROBE
On Wednesday, Strauss-Kahn's lawyers are set to defend him in a Bronx courtroom on the first day of a civil trial brought by Nafissatou Diallo, the New York maid who accused him of raping her in May 2011.
That accusation halted his career and plans to announce days later that he would run for president of France.
U.S. prosecutors dropped criminal charges, however, saying they had doubts about Diallo's credibility, and he returned to Paris.
Strauss-Kahn is now jobless and lives a life mainly behind closed doors.
Attempts to relaunch his career as an economist on the world conference circuit have been troubled. He gave a speech in China late last year but had to be bundled into a recent meeting at Britain's Cambridge University under heavy security.
Last Tuesday, he cancelled an appearance at an event in Brussels alongside the Eurogroup's Jean-Claude Junker following protests from members of the European Parliament.
($1 = 0.7504 euros) (Additional reporting by Thierry Leveque; Editing by Brian Love and Karolina Tagaris)