By Simon Carraud

BIGUGLIA, Corsica - Conservative presidential candidate Francois Fillon warned in Corsica on Saturday that France faced the same fate as debt-ridden Greece, deliberately reviving the "failing state" controversy he stoked on the Mediterranean island 10 years ago.

"I repeat what I said here in Corsica in 2007. We are a failing state... We have a debt that forces us to seek billions of euros each day on international markets," Fillon told political supporters in the island.

"France today is a country which can fall next to Spain. Portugal, Italy, even one day Greece", he added.

Fillon has based his campaign on the need to rein in spending and cut France's deficit, pledging 100 billion euros of spending cuts and 500,000 public sector job cuts, proposals that are tougher than those of any other mainstream candidate.

It was in Corsica in September 2007, as prime minister under the newly-elected president Nicolas Sarkozy, that Fillon sparked a political storm by saying he was at the head of a failing state.

"I am the head of a state that is failing on the financial front. I am at the head of a state that for 15 years has been running a huge deficit," he said at the time.

"I am at the head of state that has not voted through a balanced budget in 25 years. That cannot continue."

Although Sarkozy's government was only a few months old then, it had taken over the reins from Jacques Chirac, a fellow conservative who had ruled for two terms since 1995.

Fillon's criticism was by far the strongest of the financial performance of the Chirac era to have come from the new government at that point.

It also began a long period of friction between Fillon and Sarkozy, whom insiders say took exception to his prime minister calling himself head of state - a role that belongs to the president in France.

Fillon is struggling to get his election campaign back on track with three weeks to go, having lost the status of favorite he enjoyed after beating Sarkozy in a conservative primary last November.

Many of Sarkozy's backers took part in failed attempts to oust him from the nomination this year. Their attempts followed a scandal over allegations his wife was paid taxpayers money for work she may not have done which sent him plunging in the opinion polls.

The polls now show Fillon in third place, behind the new favorite, centrist Emmanuel Macron, and far-right National Front leader Marine Le Pen, even though recent surveys show the race tightening.

If the polls hold true for the April 23 first round, Fillon will become the first conservative candidate to be eliminated at that stage in postwar French history.

The polls show Macron beating Le Pen in the May 7 second round.

France's public debt stood at about 64 percent of GDP in 2007 when Fillon made his failed state comment, up from about 56 percent in 1995, official French figures show.

By 2015 the debt had topped 96 percent of GDP, making France the seventh most indebted country in the European Union.

(Writing by Dominique Vidalon; Editing by Andrew Callus)