Paris (AFP) - French President Emmanuel Macron's rivals on Monday warned against handing him an overwhelming parliamentary majority that would stifle debate, after his party cruised to victory in the opening round of elections to the National Assembly.
Macron's year-old centrist Republic on the Move (REM) party and its allies are tipped to clean up in the 577-member lower house of parliament, winning up to 445 seats -- an unprecedented total for a post-war president.
The opposition and French press expressed concern over what the left-wing Liberation daily called the "quasi-Stalinist result".
The leader of the rightwing Republicans in the Paris area, Valerie Pecresse, appealed for a "civic surge", warning of the risk of "groupthink".
Record low turnout of 49 percent in Sunday's first round detracted from the performance of Macron's untested team, raising concerns over the strength of his mandate.
Government spokesman Christophe Castaner admitted that voter participation -- the lowest for six decades -- was "a failure of this election" and that Macron's camp would need to reach out to those who had stayed away.
Analyst Gael Sliman of Odoxa pollsters pinned the high abstention rate on voter fatigue after the presidential election. There was also an element of those "who may not agree with Macron but do not want to block his path," he told AFP.
The result confirmed the yearning for political renewal laid bare by Macron's election.
After being routed in the first round of the presidential election, the Republicans and the Socialists, who have alternated in power for six decades, suffered further humiliation.
The Republicans were forecast to drop around half their seats while the Socialists were tipped for catastrophic losses of more than 200 seats.
Marine Le Pen's far-right National Front and the radical France Unbowed of firebrand leftist Jean-Luc Melenchon also failed to hold back Macron's tidal wave.
REM and centrist ally MoDem won 32.32 percent of the first-round vote, ahead of the Republicans and its allies on 21.56 percent and the FN on 13.20 percent.
The Socialists and their allies secured just 9.51 percent while France Unbowed and its on-off communist allies got 13.74 percent.
- 'On the ropes' -
The Republicans had hoped to rebound from their presidential defeat but have been hamstrung by infighting between those who want to cooperate with Macron, an economic liberal, and those who oppose him.
On Monday, party leaders vowed to set aside their differences for the duration of the election.
"The stakes of the second round are clear," ex-prime minister and party grandee Alain Juppe said, urging voters to get behind the opposition. "Having a monochrome parliament is never good for democratic debate," he added.
The Socialists, meanwhile, are fighting for their survival.
Only 65 of their 413 candidates remain in contention after the first round of voting, with party leader Jean-Christophe Cambadelis among the heavyweights to crash out.
"We're on the ropes, decimated, in pieces," former junior education minister Thierry Mandon said, urging the party to "give the keys to the next generation".
The loss of parliamentary seats means a loss of public funding too: one Socialist Party insider said that looked likely to fall from 28 million euros to a little less than 10 million.
Only four MPs -- two of them from Macron's slate -- topped the 50 percent mark needed for election at the first round.
REM fielded political newcomers in around 200 constituencies, some of whom felled long-sitting lawmakers on Sunday.
The FN also struggled to rebound from Le Pen's bruising defeat in the presidential run-off, with forecasts suggesting it would win a maximum of 10 seats.
Le Pen repeated her complaint that France's winner-takes-all system penalises smaller parties and called on her supporters to mobilise en masse for the second round.
- Street protests planned -
The party of France's 39-year-old president coasted to victory in Sunday's first round on the back of his strong debut.
Macron has won praise for appointing a balanced cabinet that straddles the left-right divide and taking a leading role in Europe's fight-back against US President Donald Trump on climate change.
Sunday's results show he will have a relatively free hand to push through the ambitious labour, economic and social reforms he promised on the campaign trail.
He will also have succeeded in ushering in a younger and more diverse parliament with more women and ethnic minorities.
But with many of the new lawmakers owing him their seats, analysts have warned that the next parliament could be unusually submissive.
Macron's opponents have already warned that they will take the fight to the streets.
A group of trade unions and NGOs opposed to his proposals to loosen the country's strict labour laws have called for demonstrations in several cities on June 19.