The French president Emmanuel Macron’s new centrist party looks set to take an overwhelming majority in parliament after the first round of elections held on Sunday.

Official final results released early on Monday showed Macron’s one-year-old La République En Marche (Republic on the Move) and ally MoDem winning 32.32% in the first round, ahead of Les Républicains and its allies on 21.56% and the far-right Front National on 13.20%. The Socialist party – the party of Macron’s predecessor Francois Hollande – took just 9.5% of the vote with its allies.

The result was however marred by a record low voter turnout of just 49%.

Macron’s fledgling centrist movement could, with its centrist allies, go from zero to as many as 430 seats in the 577-seat French national assembly. This would be one of the biggest majorities in France since the end of the second world war.

“France is back,” declared the prime minister, Édouard Philippe, as the news came through. “For the past month, the president has shown confidence, willingness and daring in France and on the international stage”. He called the result a vindication of Macron’s “winning strategy”.

Macron needs a solid parliamentary majority if he is to put in place his plans to loosen France’s extensive labour laws and change the French welfare system on pensions and unemployment benefits. His parliamentary candidates include a historic number of total newcomers to parliamentary politics, from an ex-bullfighter to a former fighter pilot, a mathematician and an anti-corruption magistrate as well as former local politicians – whose key campaign argument was “give the new president a chance”.

If Macron’s party does go on to win a landslide victory in the final round on 18 June, it will redraw the landscape of French politics. The traditional left and right parties that dominated parliament for decades were knocked out in the presidential election first round and their support is projected to dwindle to historic lows. Warnings by the rightwing party, Les Républicains, and the Socialist party that it would be unhealthy for democracy if Macron’s party won a “monopoly” did not appear to be heeded by voters.

How does France's parliamentary election system work? The electoral system for France's 577-seat parliament, the Assemblée Nationale, is designed to favour larger parties and make things difficult for smaller ones, who would mostly prefer proportional representation. Like the country's presidential poll, it takes place over two rounds – this year, on 11 and 18 June. It is possible for candidates to win in the first round, providing at least 25% of the voters registered in their constituency turn out and they secure more than 50% of the vote. For the remaining seats, the second round is contested by the two best-placed candidates after the first round, with any others who secured more than 12.5% of the vote.

On the right, Les Républicains and its allies are estimated by Ipsos-Steria to take between 85 and 125 seats. This would make them the biggest group in parliament after Macron’s group. But they could lose 100 of their current seats. The Socialist party had a historically bad night, expected to lose more than 200 seats and end up with just 20 to 35 seats with its allies. The Socialist party leader, Jean-Christophe Cambadélis, was knocked out of the race for a Paris parliament seat he had held for 20 years. Its unsuccessful presidential candidate, Benoît Hamon, was also outsted.

Abstention was at a record high, and Macron’s supporters will now be fighting to get voters out in the final round on 18 June to avoid accusations by political opponents that his mandate was weakened by abstention. Speculation began about why voters had not turned out. France has faced a series of elections over the past 10 months, from the party primaries on the right and left, to the two-round presidential vote. For weeks, all pollsters had predicted a foregone conclusion of huge parliamentary gains for Macron.

Jean-Luc Mélenchon’s new hard-left movement, France Unbowed, was projected to win between 11 and 21 seats – potentially able to form a parliamentary group that requires 15 deputies. Mélenchon himself will go through to a second-round run-off in a Marseille constituency, where the Socialist candidate was eliminated in the first-round. Mélenchon warned that abstention had been high among young voters, calling on them to turn out in the final round to stop Macron having “full power”.

Marine Le Pen’s far-right Front National, which came second in the presidential election with 10.6m votes, was projected to win between three and 11 seats, which the party said was “disappointing”.

The FN currently has two seats in parliament and had been seeking to reach the 15-seat threshold to form a parliamentary group that would give it more speaking time and access to top roles within the assembly. A year ago that was being presented by the party as all but inevitable. The far-right put part of the blame for its low score on the voting process, saying that without proportional representation, the odds were stacked against it. The party has been riven by internal divisions since Le Pen’s much-criticised presidential campaign, with her strategist and deputy party president Florian Philippot setting up his own grouping within the party, Les Patriotes.

Le Pen, who is attempting for the fourth time to win a parliament seat, topped the poll in the northern former coal-mining heartlands around Hénin-Beaumont in the Pas-de-Calais, and will go through to the second round, well-placed to win.

Macron’s political movement had faced setbacks during the campaign but they didn’t appear to have affected its overall tally. The small centrist MoDem party, a key Macron ally with ministers in government, was placed under a preliminary investigation on suspicion of employing fake parliamentary assistants in the European parliament. The party responded that it had “respected all rules”.

On the same day that Macron’s new government unveiled new ethics proposals to clean up politics, French prosecutors also announced a preliminary investigation into a property deal several years ago involving the partner of a minister and key Macron supporter, Richard Ferrand, who denied any wrongdoing.

The expected low turnout narrowed the second-round field, because candidates need the support of 12.5% of registered voters to qualify for the final round.