Nicolas Sarkozy's offices and home have been raided by French police as part of an investigation into claims the former president was involved in illegal political campaign financing.
Magistrates are investigating claims that staff for Liliane Bettencourt, heiress to the L'Oreal cosmetics empire and France's richest woman, gave envelopes stuffed with cash to Sarkozy aides to finance his 2007 campaign.
Mr Sarkozy is suspected of benefiting from brown envelopes of cash to help fund his 2007 campaign from Mrs Bettencourt and her late husband, André, whose former bookkeeper has told judges she withdrew 150,000 euros earmarked for Mr Sarkozy's then campaign treasurer. He also faces questioning over allegations he personally accepted cash from the Bettencourts during a visit shortly before his 2007 election. Mr Sarkozy denies wrongdoing on all accounts.
Since losing his presidential immunity following his defeat to Francois Hollande earlier this year, Mr Sarkozy is expected to face questioning in a raft of party financing and corruption cases.
In the so-called 'Karachi affair', judges are looking into irregularities in the financing of former Prime Minister Edouard Balladur's 1995 presidential campaign. Mr Sarkozy was Mr Balladur's campaign spokesman and budget minister at the time.
Magistrates suspect the Balladur camp of receiving illicit "retro-commissions" from the sale of French submarines to Pakistan. Mr Sarkozy's best man and former ministerial cabinet chief are both under formal investigation over the affair.
A separate investigation is under way into allegations that 11 French engineers died in a Karachi bombing carried out by Pakistani agents angry after bribes from the sale were cut off. Mr Sarkozy has always denied any wrongdoing.
The most recent corruption allegation to be levelled against him is that he received 50 million euros of illegal campaign contributions from the late Muammar Gaddafi.
Last month, investigative news website Mediapart published what it said was a copy of a document signed by Moussa Koussa, Col Gaddafi's intelligence chief in 2006 outlining the alleged funding deal. Mr Sarkozy has dismissed it as a forgery.
Saif-Al Islam Gaddafi, Gaddafi's son and former heir, last year unambiguously claimed that Libya had funded Mr Sarkozy's election.
Finally, he could be questioned over why his former chef de cabinet signed a lucrative contract with an opinion poll company run by a close aide of the president without going through the normal public tender procedures.