The French Prime Minister, Dominique de Villepin, has been questioned by judges for 17 hours about an alleged plot to discredit one of his political rivals.
Mr de Villepin appeared at the Paris court financial crimes section
It is only the second time in living memory that a serving French prime minister has been required to testify.
The judges say he is a star witness rather than a suspect in the so-called Clearstream scandal.
The scandal has pitted Mr de Villepin against Nicolas Sarkozy, who is tipped to run for president next year.
The questioning began on Thursday at 0900 local time (0800 GMT) and finished on Friday morning at 0300 (0200 GMT).
Apart from a one-hour lunch break, Mr de Villepin spent the rest of the time at the financial section of the criminal courts in Paris.
Speaking to reporters afterwards, he referred to his "marathon testimony," saying: "For my part, I was very pleased to be able to testify on this matter, of which I have for many months been a victim of slander and lies."
The investigation centres on bogus claims that Interior Minister Sarkozy and others were laundering kickbacks from defence deals through secret accounts with a Luxembourg finance house called Clearstream.
Mr de Villepin has vehemently denied allegations that he asked a retired secret service general to dig up dirt on Mr Sarkozy.
Media reports based on judicial leaks allege that Mr de Villepin ordered an investigation focusing on Mr Sarkozy, whose name was on the list of secret accounts. The list has since been exposed as a fake.
The judges have already questioned Defence Minister Michele Alliot-Marie - another potential presidential candidate - and former Prime Minister Jean-Pierre Raffarin.
Mr Sarkozy and Mr de Villepin are rivals for the centre-right candidacy in next year's presidential election.
However, correspondents say the affair has damaged the prime minister's chances.