Right-winger Eric Ciotti was elected as the next leader of France's formerly heavyweight conservative Les Republicains (LR) party after winning the second round ballot of party members on Sunday.
Ciotti, who is on record as saying he wants to stop what he calls a "migratory invasion" of France, won 53.7% of the votes against Bruno Retailleau, a senator who scored 46.3%, LR acting chairwoman Annie Genevard said.
Although LR and its predecessors have governed France for much of its post-war history, it has been squeezed between centrist President Emmanuel Macron on one side and the far-right National Rally of Marine Le Pen on the other.
LR's candidate in April's presidential election, Valerie Pecresse, won just 4.78% of the votes.
Ciotti, whose home base is the Nice region, is politically further to the right than outgoing LR leader Christian Jacob.
His program proposes to "rehabilitate the value of work, fight against violence and disorder in the streets, stop the migratory invasion and the rise of Islamism".
He did not rule out voting for the pension reform currently being prepared by the government.
(Reporting by Sybille de La Hamaide; Editing by Ros Russell)