The far-right National Front made only limited gains in French local elections won by a wide margin on Sunday by ex-President Nicolas Sarkozy's conservatives and their centrist allies.

Sarkozy's UMP and its allies will take over two thirds of the 102 local "departements", exit polls showed, up from 41 now, in a boost for the former president, whose recent comeback at the helm of the UMP is challenged within the party.

"The French people have massively rejected the policies of (President) Francois Hollande and his government," he told party supporters. "The time for change is now."