Former French President Nicolas Sarkozy lost his fight on Thursday against a decision by election auditors that found his conservative UMP party went over budget during his 2012 election campaign.
The Constitutional Council's ruling against him plunges the opposition UMP into financial crisis as it was ordered to return the 11 million euros ($14 million) of state money it had been advanced, as a penalty for running over budget.
It is the latest blow to the party after a tumultuous year which saw it torn in two in an acrimonious leadership struggle in the wake of Sarkozy's defeat to Socialist Francois Hollande in May 2012.
It also creates another headache for Sarkozy, who has dropped heavy hints that he is mulling a comeback for the 2017 election but has been entangled in a series of legal cases.
In a swift protest at the ruling, Sarkozy said he was quitting his post as a member of the Constitutional Council, a body which rules on constitutional issues including election disputes and automatically bestows membership to ex-presidents.
In France, election funding is capped, large donations are banned and the state subsidises campaign spending.
The council, which counted 12 members including Sarkozy, upheld a December 2012 decision by the national campaign financing watchdog that Sarkozy's campaign spending during his run-off against Hollande went over an alloted budget of 22.5 million euros.
Whereas the watchdog calculated the overspending at 300,000 euros ($389,000), the court said that Sarkozy overspent by 466,118 euros, or 2.1 percent above the ceiling.
UMP party leader Jean-Francois Cope said he would convene his team next week to examine any possible recourse.
Sarkozy is grappling with a host of legal problems, including scrutiny over the funding of his 2007 campaign. He also faces a fraud investigation over political favours, a campaign funding scandal involving France's richest woman and another involving possible kickbacks for submarine sales to Pakistan in the 1990s when he was a government minister.