The interrogation came days after his center-right UMP party beat the ruling Socialists in local elections, a victory seen as boosting Sarkozy’s prospects of running again for president.
At issue is whether it was legal for the UMP to pay the over 500,000 euros of fines he incurred for over-spending on his failed 2012 re-election campaign. In France, it is the candidate who should personally pay these fines.
Sarkozy spent about five hours at the Paris offices of the financial crimes unit, French TV channels reported.
The prosecutor’s office then announced Sarkozy had been named an “assisted witness” in the overspending case — a special status short of being placed under formal investigation but which means there is some evidence of possible implication.
Sarkozy said back in December that the repayment arranged by his UMP party had the approval of the finance ministry. He has since reimbursed the money.
After five years as president, Sarkozy ran for re-election in 2012 but lost to Socialist Francois Hollande. He bowed out of politics before engineering a comeback last year and winning the UMP leadership.
Sarkozy obtained 153,000 euros ($165,000) of state subsidies for his 2012 bid and incurred penalties of 363,615 euros for campaign overspending. Both were repaid with the help of a UMP fundraising operation that is now under scrutiny.
As part of an inquiry into the fundraising efforts started last October, the former head of the UMP, Jean-Francois Cope, and a former UMP party treasury officer, Catherine Vautrin, have been formally placed under investigation on suspicion of an illicit funding scam.
Investigators are also looking into the affairs of an events organization company called Bygmalion that they suspect of over-billing in order to raise covert money for election campaigning and have placed three UMP officials under official judicial inquiry in that case.