LREM’s landslide win in parliamentary elections earlier this month consolidated Macron’s presidential win in May.
Like Macron, most LREM lawmakers never previously held elected public office.
Some items on Macron’s agenda of far reaching pro-business reforms are already facing resistance.
Some trade unions held protests near parliament to coincide with the start of the session to voice their opposition to Macron’s plan to relax France’s stringent labour code.
“Baptism of Fire” ran the headline of conservative daily Le Figaro, in reference to the large number of political novices among the LREM.
Of its 308 deputies, only 27 served in the previous parliament.
“Will they be docile or rebellious,” the newspaper asked in its editorial.
“It’s legitimate to ask how they will react when the political climate becomes less favourable for Emmanuel Macron. This moment will inevitably come, perhaps as early as July with the contentious labour law.”
Other items on Macron’s reform agenda include a new bill designed to clean up French politics and an anti-terror law has also drawn criticism from both the right and the left, as well as from human rights groups.
The government faces one of its first big test tomorrow when the public auditor will give an update on the state of public finances.
Ministers have made no secret that they do not expect good news and anticipate broad spending cuts, blaming the previous Socialist-led government for letting the finances slip in its last months in office.
France’s other parties, including the Republicans and the former ruling Socialists, have been left deeply fragmented in the wake of Macron’s successes, which have upturned France’s political landscape.
Christian Jacob, head of the conservative Republicans in parliament, said his party were “of a mind on a certain number of bills.”
“If we agree with a bill then we’ll vote for it,” he told Europe 1 radio.
Socialist Party head Jean-Christophe Cambadelis said on Twitter that fragmentation of the National Assembly into eight political groups was “a recipe for crisis”.
LREM lawmakers picked Francois de Rugy as president of the National Assembly, a key position whose holder influences parliament’s agenda.
De Rugy is a former green politician who rallied behind Macron’s presidential bid.
Former prime minister Manuel Valls said he was leaving his Socialist party and would support LREM without being a member of it.