Topless protesters swarmed outside the French courthouse where Dominique Strauss-Kahn was due to give evidence in a trial involving orgies and an alleged prostitution ring.
Police tackled the demonstrators from the provocative group Femen as they shouted and climbed on to what appeared to be the car of the former head of the International Monetary Fund as it arrived at court in Lille.
He is due to enter the witness box for the first time in the trial, in which he is accused of taking part in an international prostitution ring set up to provide him with prostitutes for orgies at luxury hotels in France and the US, a charge he denies.
His presidential chances were ruined over an unrelated sex scandal in New York.
The French economist known widely as DSK faces up to 10 years in prison and a €1.5m fine.
The hearing began at 9.30am local time, with Strauss-Kahn dressed in a dark suit, white shirt and light grey tie.
He is on trial with 13 other defendants accused of operating a prostitution ring out of luxury hotels in Paris, Washington DC, Lille and Brussels.
Strauss-Kahn has told a French court he was unaware that women who took part in orgies at luxury hotels in Paris and Washington DC were prostitutes.
The 65-year-old and 13 co-defendants are on trial in Lille accused of aggravated pimping in connection with a sex ring centred on the Hotel Carlton in the city.
In his first testimony since the trial started on February 2, Strauss-Kahn reaffirmed his long-standing defence that he ignored the “prostitutional character” of the women who took part in his orgies.
The court has heard testimony from some of Strauss-Kahn’s fellow defendants, who include a Belgian brothel owner, local businessmen, a police officer and hotel staff accused of organising sex parties for Strauss-Kahn’s benefit.
Investigators have compiled hundreds of pages of evidence from prostitutes describing the orgies.
It is not illegal to pay for sex in France but it is against the law to solicit or to run a prostitution business.
Prostitutes questioned in the case said that between 2009 and 2011 – when the IMF chief was dealing with a global financial crisis – Strauss-Kahn was organising orgies at luxury hotels in Paris, at a restaurant in the French capital and also in Washington.