An investigating magistrate in Bordeaux, France is attempting to establish whether Sarkozy's UMP Party illegally received up to 800,000 Euros ($1,008,000) in funding for its 2007 election campaign from elderly heir to the L'Oreal fortune Lillian Bettencourt, 90.
The money would have put him over the legal funding limits for his presidential campaign, Radio France Internationale reported.
Sarkozy's campaign organizers are also accused of taking advantage of Bettencourt's age to take more money than she was aware.
Examining magistrate Jean-Michel Gentil is expected to question Sarkozy about how he obtained the funds from Bettencourt. Gentil could either charge the former president with taking advantage of someone in a position of weakness, or question him as a witness under caution, which would leave him open for other charges later, RFI reported.