French investigators have searched former President Nicolas Sarkozy's home and office.

The raids were part of a probe into suspected illegal financing of his 2007 presidential campaign by the L'Oreal cosmetics heiress, an official said on Tuesday.

Potential legal troubles have threatened Sarkozy since he lost the presidency to Socialist Francois Hollande in May elections.

Sarkozy, who lost his immunity from prosecution on June 15, denies wrongdoing.

Sarkozy's lawyer, Thierry Herzog, said the raids a day after his client had left for Canada on holiday would show nothing and that he had already supplied information to investigators that debunked suspicions of secret meetings with Bettencourt.

"These raids ... will as expected prove futile," Herzog said in a statement.

Judge Jean-Michel Gentil and other investigators from the Paris financial crimes unit conducted the search of Sarkozy's home and offices.

"Ten police accompanying the investigating magistrate raided the office of Sarkozy, raided his home and raided the home of his lawyer," said Al Jazeera's Peter Sharp, reporting from Paris.

The probe centers on the finances of France's richest woman, L'Oreal cosmetics heiress Liliane Bettencourt.

Family tension

A long-running family feud over her fortune ballooned in 2010 into a multi-layered investigation and political affair.

Allegations emerged that Bettencourt provided illegal campaign cash to Sarkozy's party during the 2007 campaign. The former president vigorously denies the claims.

The allegations struck a chord with Sarkozy's critics, who were frustrated with his handling of the recession-hit economy and saw him as too close to the rich.

An accountant for Bettencourt said in 2010 that she gave 50,000 euros in cash in 2007 to Sarkozy's party treasurer for the presidential campaign - well beyond the 4,600 euros legal limit on individual donations.

A book released last year suggested that Sarkozy himself received undeclared campaign money. But Sarkozy denies the claims.

Herzog said magistrates looking into whether Sarkozy had received campaign funds from the now mentally fragile Bettencourt had been supplied with diary details of all Sarkozy appointments in 2007.

Those details, he said, "prove that the purported 'secret meetings' with Madame Liliane Bettencourt were impossible".

The case also stirred up debate over media freedom. Le Monde filed a lawsuit accusing Sarkozy's office of using counterintelligence services to identify a source leaking information about the investigation.

Sarkozy's office said it had never given such instructions to an intelligence agency.

Source: Al Jazeera and agencies