a probe into illegal party funding as "unfair and unfounded".
In his first personal reaction to the charge laid on Thursday, Sarkozy used his Facebook page to insist he had not taken advantage of France's richest woman, Liliane Bettencourt, when she was weakened by ill health.
"I want to insist that, at no moment in my public life, did I betray the duties of my office," Sarkozy wrote.
"I will put all my energy into proving my integrity and honesty. The truth will triumph in the end. I have no doubt about that."
Sarkozy's lawyers are attempting to overturn a decision by three examining magistrates to charge him in a case threatening to destroy his hopes of a political comeback.
The former president was charged on Thursday after being summoned for face-to-face encounters with former members of Bettencourt's staff, including her butler.
The confrontation was the latest chapter in an investigation into allegations Sarkozy accepted envelopes stuffed with cash from ailing L'Oreal heiress Bettencourt to fund his 2007 election campaign.
Investigators suspect up to four million euros ($A5 million) of Bettencourt's cash made its way into the coffers of Sarkozy's UMP party. Bettencourt is now 90 and has been incapacitated since 2006, according to doctors.
Sarkozy could face up to three years in jail, a fine of 375,000 euros, and a five-year ban from public office if convicted.
He recently dropped several hints that he is considering a return to the frontline of French politics, suggesting recently he could be forced to out of a sense of duty to his country.
Against that backdrop, his lawyers have branded the decision to charge him as politically motivated.
