By 5 p.m. local time (1500 GMT), 40.75 percent had cast their ballots, the lowest turnout in the 5th Republic, compared with the same time of day in the first round of 2012, when the figure stood at 48.3 percent.
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.
"It is neither healthy nor desirable for a president who gathered only 24% of the vote in the first round of the presidentials and who was elected in the second round only by the rejection of the extreme right to benefit from a monopoly of national representation", Cambadelis said.
From five to 12 seats will be claimed by other candidates.
German Chancellor Angela Merkel congratulated Mr Macron on the "great success" of his party.
The worst losses, however, were for the Socialists of Macron's deeply unpopular predecessor Francois Hollande, who are predicted to lose around 200 seats - a historic rout that has thrown the party's future into question.
Mr Macron's Republic on the March!
Projections by three pollsters of the final outcome, based on the first round, gave Macron's movement and allies between 390 and 445 of the national assembly's 577 seats - potentially the biggest majority since president Charles De Gaulle's conservatives won more than 80 percent of seats in 1968.
While it can be considered a fairly stable rule in politics that parliamentary elections, being "second-order" are less headline-grabbing than presidential, heavily personalized ones, a failure to recognize the importance of the French legislative election will lead to a risky knowledge gap about the conditions that will define Macron's presidency over the next five years.
New Hampshire among states with GOP redistricting advantage
House seats and five more Ohio House seats in the last election than would have been expected in neutral circumstances. House elections, translating those into estimates of extra seats won because of partisan advantages.
Record-low turnout, however, took some shine off the achievement.
First-round results decided only four of the 577 seats on offer, leaving the rest to be fought out on June 18 by two or more candidates who survived elimination.
Those candidates garnering 50 percent or more of the votes in their districts will be declared the winners.
Both the Republican and Socialist parties which have traditionally governed during the time of the Fifth Republic, are likely to suffer.
Socialist Party leader Jean-Christophe Cambadelis warned that Mr Macron's party could end up "almost without any real opposition".
The result supports predictions that Macron will secure a whopping majority in the second round, thereby paving the way for him to implement his pro-business agenda.
"I prefer a small opposition", du Pique says, "It's important in a free country not to leave all the power to one man".
He needs a majority to push through the changes that he promised in his campaign.
On the diplomatic front, Macron did not lose to U.S. President Donald Trump when they postured to shake hands together at the North Atlantic Treaty Organisation summit held in Brussels late May.
In a bid to shake up the parliament, half of Macron's candidates are political newcomers who, like the president before he took the country's top job, have never held elected office.