Two judges questioned Villepin on Friday morning about an attempt in 2003-2004 to discredit France's current president, Nicolas Sarkozy, who was at the time a government minister and a political rival in the conservative UMP party, in which both men as well as former French President Jacques Chirac were members.

The judges suspect Villepin of involvement in the so-called Clearstream affair, in which Sarkozy's name was wrongly linked to an illegal bank account in Luxembourg. The preliminary charges against him were for complicity to make false accusations, receiving stolen goods, breach of trust and complicity to use false documents.

Villepin has denied breaking the law.

"I am anxious to restate this morning that at no point did I ask for an investigation into political figures, and at no moment did I partake in any political machination," Villepin said after being questioned on Friday.

The affair started in 2003 when a list of Clearstream bank-account holders surfaced who had allegedly received secret commissions from international arms sales. The list, which included the names of Sarkozy and other prominent politicians, was subsequently proven to be false.

Chirac the mastermind?

Experts retrieved documents from former intelligence chief Philippe Rondot's computer two weeks ago that suggested Villepin had instructed an associate, Jean-Louis Gergorin, to leak the list to a judge to damage Sarkozy's reputation.

Rondot had conducted a secret probe into the affair in 2004. The information on his laptop also indicated that then President Chirac had initiated the smear campaign.

Chirac has said he will not answer questions regarding the affair, claiming he remains protected by presidential immunity, a position legal experts are divided over.

Earlier this month, Gergorin, formerly the vice president of European aerospace company EADS, admitted he wrote anonymous letters to justice officials smearing Sarkozy.

Last year, Sarkozy declared himself a civil plaintiff in the suit and said he was determined to find out who tried to undermine him.