The leftists could now be on on track for gains in the run-off voting March 16, reversing defeats in the last municipal voting in 2001.
'Warning sent' Francois Hollande, the Socialist leader, said voters had sent "a warning to the president of the republic and the government on the policies conducted over the past nine months".
"Everything remains open. Nothing has been won or lost"
Francois Hollande, Socialist leader |
However, he admitted that until next week's run-off: "Everything remains open. Nothing has been won or lost."
The Socialists retained a firm grip on the capital Paris and cemented their hold on France's third city Lyon - clinching victory in round one - as well as on the northern city of Lille.
They also appeared well-placed to seize the eastern city of Strasbourg, one of three trophies up for grabs along with the second city Marseille on the Mediterranean and southwestern Toulouse.
Voters are choosing mayors and other local leaders in more than 36,000 towns and cities nationwide.
Segolene Royal, the defeated Socialist presidential candidate who had urged voters to "punish" Sarkozy's government, called on them to keep up the pressure in round two.
Plummeting approval The symbolic loss of one or more major city could further damage Sarkozy's reputation and undermine his ability to push through widespread changes.
Sarkozy's approval rating has plummeted from 67 per cent in July last year to around 33 per cent of the electorate.
His divorce from his second wife Cecilia, followed by a swift marriage to supermodel and singer Carla Bruni, gave many voters the impression he was neglecting their concerns.
French consumer confidence is also stuck at a 21-year low, despite a fall in unemployment to 7.5 per cent, its lowest level in more than two decades.
Francois Fillon, the prime minister, accused the opposition of "mixing up local and national issues" during the campaign, but on Sunday Patrick Devedjian, UMP chief, admitted that the results were "not good".