French magistrates have handed former president Nicolas Sarkozy preliminary charges over suspected illegal overspending on his failed 2012 re-election campaign.

France had a ceiling on presidential campaign funding in 2012 of €22.5 million.

Conservative Mr Sarkozy, who was president from 2007-2012 and lost that year's election to Socialist Francois Hollande, is accused of spending €17 million over that limit.

Mr Sarkozy, now France's main opposition leader, was questioned by judges investigating the invoice system his party and a company named Bygmalion allegedly used to conceal unauthorised overspending. His party was then called UMP but has since renamed itself the Republicans.

The Paris prosecutor's office said Mr Sarkozy was handed preliminary charges of alleged illegal campaign finance, and could later face fraud charges.

Preliminary charges mean magistrates have strong reason to believe a crime was committed but give them more time to investigate before deciding whether to send suspects to trial.

Several people close to Mr Sarkozy, including his former top adviser, face preliminary charges in the case. The former president has already been fined €364,000 for overspending in the case.

It is one of several legal cases in which his name has surfaced.

Mr Sarkozy had already been given preliminary charges in another case, accused of corruption and influence-peddling based on information gleaned from phone taps. He has not been convicted of wrongdoing or gone to trial.