French police have raided the home and offices of the former French president Nicolas Sarkozy as part of an investigation into illegal campaign financing and alleged brown envelopes of cash from France's wealthiest woman, the L'Oreal hairspray heiress Liliane Bettencourt.

Police searched the mansion rented by Carla Bruni in a chic gated community in the west of Paris, where she and Sarkozy live with Bruni's 11-year-old son and the couple's new baby daughter. Officers also searched the office of the legal firm where Sarkozy is a partner and the new office he moved into after losing the presidential election to Socialist Francois Hollande in May.

The Sarkozys were not present as they had left for a Quebec chalet holiday on Monday, Sarkozy's lawyer said.

As president, Sarkozy had judicial immunity which protected him from legal investigations, but this expired on 16 June.

A judge in Bordeaux is currently investigating whether Sarkozy's right-wing UMP party benefited from envelopes of cash from the ageing and mentally fragile Bettencourt, during Sarkozy's successful election campaign in 2007. The investigating magistrate is trying to establish whether Sarkozy's campaign might have received euro 800,000 in illegal funding, and whether transfers from Swiss accounts may have been handed over to Sarkozy's campaign treasurer or even to Sarkozy himself.

In February, Eric Woerth, the former French budget minister and treasurer of Sarkozy's ruling UMP party, was placed under judicial investigation over cash he was alleged to have received from the billionaire Bettencourt to fund the 2007 campaign. He denies any wrongdoing.

The investigation is part of the wider Bettencourt saga, which has gripped France for years with plot-twists including a disgruntled butler who hid a tape-recorder in the drawing room, and, crucially, security services at the head of the French state which might have spied on journalists to hush it all up.

Sarkozy's lawyer, Thierry Herzog, said the raids 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.

Herzog said magistrates looking into whether Sarkozy had received campaign funds from 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".

Sarkozy, 57, who has taken a low profile since his defeat, could come under the spotlight in a number of legal cases now that he is no longer head of state.

He could also become a focus of the separate investigation into whether or not there was a shady "cabinet noir" at the highest reaches of the French government which used the secret services to spy on journalists at Le Monde to uncover their sources for stories about the Bettencourt affair. A security chief and Sarkozy ally has been placed under investigation in the alleged political spying scandal. Sarkozy has denied any links to the case.