The governing Socialists in France have suffered a heavy defeat in the second and decisive round of local elections.
Prime Minister Jean-Marc Ayrault acknowledged that many voters had lost confidence in the government and promised their clear message would be heard.
The opposition UMP party is claiming victory, while the far right celebrating further gains, the BBC reports.
UMP leader Jean-Francois Cope hailed what he called a "blue wave" of support for his centre-right party. The far-right National Front was heading for victory in up to 15 towns, partial results indicated.
The Socialists have been hit by growing discontent over the economy. Mr Ayrault acknowledged the vote was "a defeat for the government and the [Socialist] majority".
"This message is clear... The president will draw conclusions, and he will do so in the interest of France,'' he added, in an apparent reference to a likely cabinet reshuffle.
It was unclear when a new government might be announced or if Mr Ayrault would keep his job.
French President Francois Hollande is due to meet Interior Minister Manuel Valls on Monday morning, and later Mr Ayrault.
The Socialists were said to have lost 155 towns of more than 9000 inhabitants, Mr Valls said late on Sunday.
Turnout in Sunday's second-round vote was low, which was bad news for President Francois Hollande's Socialists as it was their supporters who were not voting, the BBC reports.
Marine Le Pen's National Front was on course for victory in the southern towns of Beziers and Frejus and in Villers-Cotterets, north-east of Paris.
The party has also captured the 7th district of Marseille, France's second largest city. The district has a population of about 150,000, which makes it the party's biggest win.
The UMP was said to have captured a number of key cities including Toulouse, Quimper, Limoges, Saint-Etienne, Reims, Roubaix and Tourcoing.
The Socialists retained control of Paris, with candidate Anne Hidalgo due to become the capital's first female mayor.