Five aides and allies of former president Nicolas Sarkozy went on trial on Monday accused of having misused public money and cronyism, adding to the former head of state's legal problems.
Sarkozy's former chief of staff Claude Gueant and former adviser and consultant Patrick Buisson are among those charged over multimillion-euro contracts for polling services.
Prosecutors say the contracts signed by Sarkozy's staff during his 2007-2012 term in office were sealed in secret and without competition, breaking French laws on public financing that require transparency and bidding.
The other accused, who face charges including favouritism, conspiracy and misusing public funds, are former aides Emmanuelle Mignon and Julien Vaulpre, and former polling expert and consultant Pierre Giacometti.
The case illustrates "the way in which Nicolas Sarkozy governed, using the presidency and state resources for his personal interests, worrying foremost about his image and his re-election to the detriment of the law", a lawyer for anti-corruption group Anticor, Jerome Karsenti, said before the trial.
The accused deny the charges. Sarkozy has said he will not appear as a witness.
Proceedings were adjourned two hours after they started on Monday, with the judge set to rule on Tuesday whether to force Sarkozy to testify.
In late September, a French court handed the former right-wing leader a one-year prison sentence for illegal financing of his 2012 re-election bid, seven months after he received a separate jail term for corruption.
Sarkozy, 66, who is appealing against both sentences, is not expected to serve time behind bars, with the courts ruling that he can wear an electronic bracelet at home instead.
He has promised to clear his name and has accused French prosecutors of a "witch hunt".
Sarkozy has also been charged over allegations that he received millions of euros for his 2007 election campaign from the late Libyan dictator Muammar Qaddafi.
