President urges voters to get on the move after his party’s strong showing in first round of parliamentary elections is tempered by record low turnout

Emmanuel Macron’s fledging centrist party La République En Marche has launched a drive to get voters out in the second round of the French parliamentary elections after its very strong first round showing was marred by a record low turnout.

“France is back,” the prime minister, Édouard Philippe, declared triumphantly after first round voting on Sunday put La REM on course for a crushing victory and an overwhelming parliamentary majority, as the traditional parties that once dominated French politics took a drubbing.

Less than half of voters cast their ballots, however, raising fears that the president’s mandate could be weakened by a lack of participation.

Macron’s movement and its smaller ally MoDem are projected to be within reach of as many as three-quarters of the 577 seats in parliament. Projections show it could take between 400 and 445, which would be one of the biggest majorities in the modern French state.

The scale of the potential landslide demonstrates the extent to which Macron, a newcomer to party politics, has managed to transform the French political landscape in record time. Sixteen months ago, La REM didn’t exist. Now it is set to dominate legislation and win a vast injection of subsidies.

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.

Other political figures were wary of Macron’s expected parliamentary monopoly. Alain Juppé, the centre-right mayor of Bordeaux, said “having a monochrome parliament is never good for democratic debate”. It was not clear how opposition parties would be able to stem much of Macron’s advance in Sunday’s final round.

Government spokesman Christophe Castaner said the 49% turnout - the lowest for six decades in a parliamentary vote - was “a failure of this election”. Macron’s camp immediately said it would need to reach out to those who stayed away.

The biggest loser of the night was the Socialist party, which saw its support plummet, prompting talk of carnage and massacre. The party is on track to lose at least 200 seats, and much of its funding.

A swath of senior Socialists, including former government ministers, lost their seats in the first round. The party leader, Jean-Christophe Cambadélis, lost the Paris seat he had held for 20 years. The Socialists were left without a single candidate in the running in its one-time northern heartlands of Pas-de-Calais and the Seine-Saint-Denis suburbs north of Paris.

The right, which only a year ago had seen the presidential and parliamentary elections as “impossible to lose”, also faces a disappointing result and could be on track for its worst parliamentary score in France’s postwar Fifth Republic on Sunday. Les Républicains could see its number of seats shrink from 199 to between 70 and 130. It faces a difficult battle in the second round, even in its historic bastions of western Paris.

The far-right Front National came third with about 13% of the vote, far below expectations. Its leader, Marine Le Pen, failed to capitalise on the 10.6m votes she won when she came second in the presidential election last month.

The FN, which has two parliamentary seats, was 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. Now, however, it is likely to reach at best a handful of seats. At worst it could be left with only one seat. Although the FN is present in run-offs in 118 constituencies, it faces the time-old issue of voters on the right and left joining to keep it out.

Jean-Luc Mélenchon’s hard-left movement, France Unbowed, is projected to win between 11 and 23 seats – potentially enough to form a parliamentary group - but it is not big enough to claim to be the main opposition force against Macron as it had intended. Mélenchon himself will go through to a second round runoff in a Marseille constituency, where the Socialist candidate was eliminated in the first round. Mélenchon said abstention had been high among young voters, calling them to turn out in the final round to stop Macron having “full power”.

Macron’s opponents blamed him for the low turnout, but polling indicated that abstention was highest among Le Pen and Mélenchon voters. Young and working-class voters abstained in high numbers. In Guadaloupe, abstention reached 76%. It was also high in poor areas of mainland France, including the northern Paris suburbs, parts of Marseille, and parts of the de-industrialised north-east.

Macron’s domination of parliament could give him a relatively free rein to push through his plans to loosen France’s extensive labour laws and change the welfare system on pensions and unemployment benefits.

The German chancellor, Angela Merkel, congratulated Macron on a “great success” on Sunday, calling it “a vote for reforms”.