Benoit Hamon says he will launch his new leftwing movement would be launched on July 1

French Socialist presidential candidate Benoit Hamon, who crashed out of the election's first round, said Wednesday he plans to launch a new leftwing movement.

Hamon vowed to "rebuild the left" while remaining a member of the outgoing Socialist Party, crippled by deep ideological divisions.

"I invite men and women who belong to political parties or who do not. I invite them to continue this essential work to rebuild the left," Hamon said.

He said the "broad-based" movement would be launched on July 1.

Hamon was the surprise winner of the Socialist nomination for the presidential election, beating former prime minister Manuel Valls.

But his leftwing policies, and his association with unpopular outgoing President Francois Hollande, proved unpalatable to voters and he scored just 6.4 percent of the first-round vote in April, being overtaken by Communist-backed Jean-Luc Melenchon.

The election, resoundingly won by centrist Emmanuel Macron on May 7 over far-right candidate Marine Le Pen, was the first time since 1958 that neither of France's main left or right parties reached the second round.