A French probe on Wednesday charged a former minister close to President Nicolas Sarkozy with influence peddling but did not immediately uphold more potentially damaging charges of illegal campaign financing.

Eric Woerth, formerly Sarkozy's budget minister and treasurer of his UMP party, was charged after he was grilled for hours about the alleged influence peddling and alleged illegal campaign donations by L'Oreal heiress Liliane Bettencourt.

"Mr Eric Woerth testified today from 9:30 am in the framework of the judicial investigation" into the charges, prosecutors in Bordeaux, where the probe is being conducted, said in a statement.

"At the end of this hearing, which concluded at 9:50 pm, he was charged with passive influence peddling," which is punishable by up to 10 years in prison and a 150,000 euro ($199,000) fine, the statement said.

The influence peddling charges are likely to relate to allegations Woerth secured the Legion of Honour, France's highest award, for Bettencourt's financial manager, Patrice de Maistre, after he secured a job for Woerth's wife to help manage the heiress's fortune.

The investigating judges did not, however, immediately go forward with the campaign financing charges related to Bettencourt.

Bettencourt, France's richest woman, is at the centre of a series of long-standing, overlapping legal inquiries, including one into claims she showered leading right-wing figures with envelopes stuffed with undeclared campaign donations.

Bettencourt's accountant, Claire Thibout, has testified to having provided 50,000 euros in cash to Maistre, which was then handed over to Woerth for Sarkozy's campaign.

She had allegedly been asked to provide 150,000 euros but did not have the cash at hand. Under France's electoral code, individual election campaign contributions may not exceed 4,600 euros.

Woerth left the government in 2010 and in 2011 police carried out searches of his home and the UMP's offices in connection with the case.

He has strongly denied the allegations.

The case is only one of several corruption investigations plaguing Sarkozy as he prepares for a tough re-election fight against Socialist flag-bearer Francois Hollande in a two-round vote in April and May.

Sarkozy, who as president is immune from criminal prosecution, has fiercely denied any personal wrongdoing.