By Ingrid Melander
PARIS (Reuters) - France's far-right National Front is expected to strengthen its hold on grassroots politics in a second round of local elections on Sunday that ex-president Nicolas Sarkozy's conservatives are forecast to win.
Marine Le Pen's anti-immigrant, anti-euro FN party aims to build a base of locally elected officials to become more mainstream and thus better placed to contest national ballots.
In a setback to its claims to have become France's leading party, the FN placed second last week in the first round of the local elections, but it did win one in four votes and is all but certain to see a big jump from its current two councillors.
"The FN has now put down roots nationwide, it has reached a level that is high, too high," French Prime Minister Manuel Valls, a Socialist, told Le Journal du Dimanche weekly.
Valls, whose deeply unpopular government is trying to play up modest signs of recovery in the euro zone's second largest economy, has stressed his "fear" of the FN's rise in an attempt to mobilise left-wing voters.
The second round is also a key test for Sarkozy, who has put a shaky political comeback back on track by steering his conservative UMP party and its allies to an unexpected victory in the first round but still faces resistance within his party.
Opinion polls see the UMP and its allies winning the local elections with nearly twice as many seats as President Francois Hollande's Socialists and their allies.
The polls see the Socialists losing 20 to 40 of the 61 "departments" they now hold, but Valls said his government would press on with reforms to tackle France's economic stagnation, adding that a cabinet reshuffle was not on the cards for now.
The FN, which topped last year's European Parliament elections in France, had eight of its candidates elected in the first round of the local polls and could see as many as 220 more elected on Sunday, an Ifop poll showed. That would be far fewer than the mainstream parties but a big jump from all past elections in the "departments" councils.
The far-right party is hoping to win one or two departments at most due to unfavourable electoral arithmetic but it is eyeing a bigger win in regional polls later this year. Surveys also show that Le Pen is likely to make it to the second round of France's presidential election in 2017, but not winning.
The complex election system, in which a duo of councillors is elected per constituency who then elect the presidents of 98 "departments'" councils, means it may take time to form a clear picture of how many councils each party has won.
In total, 4,108 councillors with limited powers over roads, schools and social services will be elected. At 1700 (1100 EDT), voter turnout stood at 41.94 percent, nearly six points higher than in the previous local elections in 2011.
(Additional reporting by Jean-Baptiste Vey; Editing by Gareth Jones)