France's far-right National Front (FN) has failed to win a single region in the second round of elections, despite record results in the first.
The loss is a disappointment for National Front leader Marine Le Pen, who had hoped to use regional election wins as a springboard for presidential and general elections in 2017.
The conservatives won seven constituencies and the socialists five in the regional run-off on Sunday.
Although it won no region, the FN still recorded its best showing in its history and Le Pen gave a defiant speech to supporters, saying "nothing can stop us now".
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Tactical voting by socialist voters kept the National Front at bay.
After first-round election results saw the FN win more votes than any other party nationally, the Socialist party withdrew its candidates in the north where Le Pen was the main candidate, and in the southeast where her niece Marion Marechal-Le Pen was running, urging supporters to vote for Sarkozy to keep FN out of power.
"Tonight, there is no place for relief or triumphalism," Socialist Prime Minister Manuel Valls said. "The danger posed by the far right has not gone away; far from it."
Sarkozy struck a similar theme, calling the strong FN showing a "warning sent to all politicians, ourselves included, in the first round".
"We now have to take the time for in-depth debates about what worries the French, who expect strong and precise answers," he said, citing Europe, unemployment, security and national identity issues.
The Socialist party languished behind the FN and the Republicans in the first round of the vote, which was held under a state of emergency only three weeks after 130 people were killed in the ISIL-claimed attacks in Paris.
"Voter apathy in the first round had worked in the National Front’s favour," Al Jazeera's Jacky Rowland, reporting from Paris, said. "But the turnout this Sunday was considerably higher, with nearly 60 percent taking part."
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Source: Al Jazeera and agencies