Leftwing outsider Benoit Hamon will fight former prime minister Manuel Valls for the French Socialist presidential nomination next Sunday, January 29, after winning the first round of the party's primary, AFP reports.

Hamon was not considered a serious contender when the campaign began in December but the 49-year-old former education minister put himself in the driving seat with what he called a "message of hope and renewal."

With Europe shifting to the right and the deeply unpopular President Francois Hollande ruling himself out, the Socialist primary has been billed as a fight for the party's soul with a left-leaning faction represented by Hamon battling Valls' centrist camp.

Hamon, 49, scored over 36 percent with Valls trailing on 31 percent, according to results from around 80 percent of polling stations.

Maverick former economy minister Arnaud Montebourg was eliminated with 17 percent and immediately threw his support behind Hamon.

Whoever wins the Socialist nomination faces long odds as polls currently show the presidential election coming down to a contest between conservative ex-premier Francois Fillon, far-right leader Marine Le Pen and Emmanuel Macron, the 39-year-old former economy minister.