The scale of Macron's absolute majority shows the extent to which the new president, a newcomer to party politics, has managed to transform the French political landscape in record time.
She said they will especially fight against what she called Macron's pro-European, pro-migrant policies. She said although Macon now has a majority in parliament, his ideas are a "minority" and said the Front National will fight his reform plans.
With 57% of votes counted, the Interior Ministry said that Mr Macron's party had won 4% of the vote, followed by the conservative Republicans with 23%.
Turn-out was also thought to be down.
The conservative party had enough seats to "defend its convictions", said the party's leader for the elections, Francois Baroin, calling on Macron to heed the record low turnout, which he said sent "a message".
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.
The result means that Macron should be able to push through both Prime Minister Philippe's government as well as proposed liberalizing reforms that are opposed by both parties on the left and the far-right National Front.
But turnout was estimated to be extremely low, at around 44 percent, giving his critics grounds to claim he has no groundswell of support. According to estimates from the second and final round of votes on Sunday, La République en March and its ally, the centrist Democratic Movement party, won 361 out of 577 seats-slightly lower than the crushing 400-plus majority that they had been slated to win.
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Le Pen entered parliament for the first time in her career in one of at least eight seats the FN won, but the party was set to fall well short of its 15-seat target.
The Socialists, who ruled the nation before Mr Macron's independent presidential victory in May, were decimated and only won 6% of the vote. President Emmanuel Macron's fledgling Republic on the Move! party is hoping for a steamroller win in this election that would upend years of French political expectations.
"The rout of the Socialist Party is undeniable", said PS leader Jean-Christophe Cambadelis, who humiliatingly lost his seat in the first round.
Melenchon also honed in on the record low turnout, saying: "The French people are now engaged in a sort of civic general strike".
This is well down from 46.42 percent seen in the 2012 election and 40.75 percent in the first round of voting in these legislative elections on June 11.
In the first round, about 49 percent of those registered to vote cast ballots.
Macron's party "vampirized" the left and right after his huge win in the presidential ballot, Dabi said on CNews TV.
Far-left ex-presidential candidate Jean-Luc Melenchon is voting in the Mediterranean city of Marseille, where he is seeking a seat as well. Experts partly blamed voter fatigue following the May election of Macron, plus voter disappointment with politics.
The strong mandate would also give the 39-year-old president a free hand to move fast with promised legislation, notably on changing labor laws to make hiring and firing easier.
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