French President Emmanuel Macron put a group of relative unknowns, some from outside politics, into ministerial roles on Wednesday to replace those that left under a cloud just weeks into his tenure.

The new appointments came as France's main conservative party splintered under the impact of Macron's sudden rise to presidential and parliamentary power, and the seismic shift it has caused continues to reverberate around French politics.

Businesswoman Florence Parly, who worked previously in a Socialist government and for major French transport companies, was named defence minister, and law expert Nicole Belloubet was nominated justice minister, replacing two of the departed.

Jacques Mezard moved from the Agriculture Ministry to the territorial planning ministry vacated by Macron's right-hand man Richard Ferrand earlier this week. Macron loyalist Stephane Travert took over the agriculture portfolio.

Macron's reshuffle, tapping more people from the non-political world, reflects the profile of many of his newly elected members of parliament.

It also keeps a fragile balance of people from left, right and centre and has one more women than men.

The reshuffle came after a group of ministers from an affiliated centrist party, MoDem, resigned over allegations the party misused European parliamentary funds.

Those who departed the justice and defence ministries were, respectively, Francois Bayrou, MoDem party leader, and Sylvie Goulard - who had been seen as a key plank of Macron's plan for closer ties with Germany.

Bayrou, a Macron ally since endorsing his centrist bid for the presidency in February, said he quit to protect the government from the scandal that has engulfed him.

"I will stand by the president and faithfully support him with a political and personal understanding that is dear to me," Bayrou told journalists.

UNDER INVESTIGATION

His centre-right party is embroiled in a judicial probe into claims it misused EU parliamentary funds, and its importance as a Macron ally waned after his Republic on the Move (LREM) party won a big majority in Sunday's parliamentary election. The majority is so large that Macron does not need MoDem to get planned pro-business labour reforms through parliament.

Earlier on Wednesday his camp was in upbeat mood.

"It simplifies things," government spokesman Christophe Castaner said on Europe 1 radio. "We have a majority after Sunday's big win and we have the wherewithal to govern. So now it's time to get to work."

MoDem's departure, however, risks unbalancing Macron's carefully crafted government of the left, right and centre, which broke with convention as he extended his support base.

But in a further sign of how Macron has dismantled France's traditional left-right divide, a lawmaker from the main conservative Republicans party said he was forming a splinter group that would back the president on some reforms.

"We're working on the creation of ... a new force in parliament," Thierry Solere told reporters, adding that the roughly 40-strong group would include Republicans and legislators from the Union of Democrats and Independents.

Macron's LREM won 308 seats in the 577-strong National Assembly on Sunday, while MoDem gained 42.

Goulard, a European expert well known in Brussels and Berlin, had emphasised her pro-EU push and desire to work towards greater defence integration.

"No other French politician knew how to talk to the Germans in quite the same way. With her goes the hope of more integration in the defence sector. At least for now," said Britain-based think-tank Eurointelligence.