Others said they had not voted as they were exhausted out by the drawn-out electoral cycle, with party primaries that started past year before the two rounds of presidential and then legislative contests.
The party's chief Jean-Christophe Cambadelis and its failed presidential candidate Benoit Hamon both crashed out of the running on Sunday.
PM Philippe admitted the "demobilisation" of voters but said that it was because the "presidential election "ended the debate" about France's political direction and that "some political forces were unable to find new energy" after the presidential vote".
Returns showed that the National Front would take about 13.5 percent of the vote, while Jean-Luc Mélenchon's leftist France Unbowed Party was expected to win just 11 percent. The Socialist Party, which was the majority party in the outgoing assembly, would get only 20 and 30 seats.
Mr Macron's Republic on the March!
The French political system has not been as polarized as our own, but it's not far off: The prior Assembly was split largely between the country's two major parties, the Socialists and the Republicans, who together occupied more than 80 percent of the seats.
French government junior minister Mounir Mahjoubi said voters want to give a large majority to the new president following partial results showing his new centrist party is clearly leading the first round of France's parliamentary elections.More news: Gulf states to mark end of Ramadan from Sunday
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Sunday's vote in France saw the lowest turnout (about 50%) since 1958.
If no candidate manages to achieve that target, then all candidates who won at least 12.5% of registered voters go to the second round, where the victor will advance to Parliament.
Pollsters' projected that as many as one-third of votes went to Mr Macron's camp in the first stage of the two-part election.
Pegard says even though they didn't initially support Macron, he's won them over. One stunning upset was that of the socialist party leader to 33-year-old Mounir Mahjoubi, Macron's new digital affairs minister and the son of Moroccan immigrants.
The projections from Sunday's voting show Macron's Republic on the Move movement is in strong position to win the decisive second round vote June 18.
He said that a "reaction is indispensable" in order to have a "balanced power" in the assembly. Unlike Macron, however, they came from long-established political parties with developed electoral apparatuses.
Mr Macron, 39, needs a majority to push through the changes that he promised in his campaign.
Le Pen and other opposition figures chose instead to highlight the abstention rate, which the National Front leader described as "catastrophic", calling on "patriots" to turn out "massively" in next Sunday's second round, which will fill most of the assembly's seats.
The former investment banker who had never held elected office before becoming president will also have succeeded in ushering in a younger and more diverse parliament with more women and ethnic minorities.