By Ingrid Melander and Leigh Thomas
PARIS (Reuters) - President Emmanuel Macron won a commanding majority in France's parliamentary election on Sunday, sweeping aside traditional parties and securing a powerful mandate for pro-business reforms.
The result, based on official figures and pollster projections, redraws France's political landscape, humiliating the Socialist and conservative parties that alternated in power for decades until Macron's election in May.
Three pollsters projected that Macron's Republic on the Move (LREM) and its Modem allies would win 355 to 365 seats in the 577-seat lower house, fewer than previously forecast.
They predicted the conservative Republicans and their allies would form the largest opposition bloc with 125 to 131 seats, while the Socialist Party, in power for the past five years, and its partners would secure 41 to 49 seats, their lowest ever in the postwar Fifth Republic.
Official figures with 90 seats still left to be decided showed LREM had already won its majority.
"This is an opportunity for France. One year ago no one would have imagined such a political renewal," Prime Minister Edouard Philippe said in a statement.
Voter turnout was projected to be a record low at about 42 percent.
The high abstention rate underlines that Macron will have to tread carefully with reforms in a country with muscular trade unions and a history of street protests that have forced many a past government to dilute new legislation.
Government spokesman Christophe Castaner said it signaled voters "had not wanted to hand Macron a blank check."
Nevertheless, the scale of victory gives the president, a pro-European Union centrist, a strong platform from which to make good on campaign promises to revive France's fortunes by cleaning up politics and relaxing regulations that investors say shackle the euro zone’s second-biggest economy.
Victory for Macron, France's youngest leader since Napoleon, marks the routing of the old political class.
Having never held elected office, he seized on the growing resentment toward a political elite perceived as out of touch, and on public frustration at its failure to create jobs and spur stronger growth, to win the presidency.
His year-old party then filled the political space created by the disarray within the Socialist Party and the Republicans, with Sunday night capping a sequence of events that a year ago looked improbable.
"Tonight, the collapse of the Socialist Party is beyond doubt. The president of the Republic has all the powers," Jean-Christophe Cambadelis said after announcing he would step down as Socialist Party chief.
He said the party would have to rebuild itself from the top down. Cambadelis was knocked out of the running for parliament in last week's first round of voting.
Far-right leader Marine Le Pen won a seat in the National Assembly for the first time. Her National Front party clinched at least eight seats in total, a result she celebrated but which may disappoint supporters who a month ago dreamed of entering the Elysee.
"We are the only force of resistance to the dilution of France, its social model and identity," Le Pen said in a televised address in her northern fiefdom of Henin-Beaumont.
"We shall fight with all our strength the harmful projects of the government, which is only in place to implement the road map sent by Brussels."
Francois Baroin, who led the Republicans' campaign, said the conservatives would emphasize their differences with Macron, especially on taxes.
The scale of LREM's projected win means Macron will enjoy an absolute majority even without the support of alliance partner Francois Bayrou and Modem, lending him a freer hand for reforms and room for a government reshuffle should he choose to carry one out. Modem currently has two ministers in the Cabinet.
Macron's rivals went into the second round trying only to limit the scale of the newcomer's win. They urged voters not to allow too much power to be concentrated in the hands of one party and warned Macron's MPs would be mere yes-men who would rubber-stamp legislation.
It appeared the message had some impact. Opinion polls before the vote had projected Macron could win as many as 470 seats.
Far-left leader Jean-Luc Melenchon, who won his Marseille seat, promised "social resistance" to Macron's reform agenda and said the high abstention rate meant the president lacked the legitimacy to destroy the labor code.
Melenchon's resurgent France Unbowed and the Communist Party were on course to win 26 to 30 seats. In a combative speech, which contrasted sharply with the defeated tone of the Socialist Party, Melenchon reached out to disappointed left-wingers.
"It is France Unbowed which will call the country, when the moment comes, to social resistance," Melenchon said. "I hereby inform the new powers that not a foot of ground will be given up in the labor law struggle."
(Additional reporting by Paris newsroom; Writing by Richard Lough; Editing by Susan Fenton and Peter Cooney)