Roland Dumas: His mistresses received Elf cash, court heard

Mr Vichnievsky is investigating the sale of six French frigates to Taiwan in 1991, a contract which was allegedly approved by the government after bribes were paid by Mr Sirven.

Mr Sirven has been in custody since he was arrested in the Philippines in February after four years on the run.

He has already been questioned once over his and Elf's role in the frigates deal, but did not give clear answers.

A second French company, Thomson-CSF, manufactured the frigates, but Elf allegedly lobbied the government on the firm's behalf to ensure the deal was not blocked.

Christine Deviers-Joncour: Allegedly paid by Elf to influence government

Mr Sirven is suspected of paying Christine Deviers-Jonour - then Mr Dumas' mistress - to win his backing for the deal.

Mr Sirven's trial, which ended last month, steered clear of the frigate issue, focusing instead on Elf's own business interests.

The court heard evidence that Mr Sirven had controlled a $400m slush fund, which paid Ms Deviers-Joncour huge sums of money to influence Mr Dumas on Elf's behalf.

A verdict on the first trial is due on May 30.

Fresh arrests

Elf, a French state company at the time of the alleged scandal, was taken over last year by the Franco-Belgian group TotalFina.

Earlier this week, reports from Switzerland said three businessmen had been indicted for allegedly laundering stolen funds hidden away by Mr Sirven.

The case is reported to involve more than 50m Swiss francs ($27m).