The unprecedented step followed the arrest of Sarkozy's lawyer and two magistrates who are under investigation for allegedly using their influence to obtain information about legal cases against him.
Detectives are trying to establish whether the former leader promised a top-level job in Monaco to a magistrate in return for letting him know whether corruption allegations against him would go to court. Sarkozy denies any wrongdoing.
The police move on Tuesday represents a blow to Sarkozy's hopes of making a political comeback in 2017.
The former leader of the UMP is said to have been hoping to profit from the disarray and lack of leadership in his center-right party, which is itself mired in legal investigations, to stand for president again.
Christian Estrosi, the mayor of Nice and an MP for the UMP party, rushed to defend Sarkozy on Tuesday. "Never has a former president been subjected to such treatment, such an outburst of hatred," he tweeted.
Government spokesman Stéphane Le Foll denied there had been any political pressure behind the move to question Sarkozy.
"The justice system is investigating and will follow this through to the end. Nicolas Sarkozy can face justice just like anyone else," Le Foll said.
It is alleged that information obtained from tapping the former leader's phone conversations with his lawyer, Thierry Herzog, a controversial and unusual step, suggested there had been what was referred to as a "traffic of influence".
Police were listening to Sarkozy's calls as part of a separate investigation into claims he accepted illegal donations from the former Libyan dictator Muammar Gaddafi for his 2007 presidential election campaign.
Sarkozy served one term in office before being beaten by the Socialist candidate, François Hollande, in 2012.
SHI/SHI