France's centrist government faces confidence votes from both the left and right Tuesday over the damaging scandal surrounding a top aide to President Emmanuel Macron who was filmed manhandling demonstrators.

Since Macron's Republic On The Move (LREM) party holds a comfortable majority in the lower-house National Assembly, the two votes have no chance of bringing down the government.

But they condemn what opposition lawmakers call a "constitutional crisis" over revelations that Macron's office knew that a top security aide, Alexandre Benalla, had roughed up protesters during May Day demonstrations in Paris.

Alleging an attempted cover-up, opposition parties are demanding that the government "explain itself" over the worst scandal since Macron took office in May last year.

Numerous senior officials have already been hauled before parliamentary commissions over their responses to the affair, with LREM chief Christophe Castaner the latest to appear on Tuesday.

Macron has dismissed the scandal as a "storm in a teacup" but his opponents have continued to heap criticism on his handling of it, demanding he address the nation.

Christian Jacob of the rightwing Republicans has accused Macron of "monarchical leanings" and disrespect for the balance of power, while leftwing firebrand Jean-Luc Melenchon has urged a "return to order".

Benalla, Macron's 26-year-old former chief bodyguard, has been charged with assault and impersonating an officer after he was filmed hitting a protester and wrestling another while wearing a police helmet.

- New allegations -

On Monday prosecutors opened a new investigation over allegations from two more protesters that Benalla also manhandled them, hours before the incident that sparked the scandal.

Benalla was initially suspended for two weeks from his job and stripped of some of his responsibilities over the May Day incident.

He was finally sacked this month after Le Monde published videos of him at the demo.

In several media interviews he has insisted that he was trying to help the police by bringing aggressive demonstrators under control, and that he himself did not use violence.

He was wearing a helmet that he was given for his own protection while attending the protest as an observer, he added.

Prime Minister Edouard Philippe is set to respond to speeches by the two MPs presenting the motions, led by the Republicans and the Communist Party, starting at 1300 GMT.

LREM lawmakers have dismissed the votes as an attempt to derail Macron's reform drive, with the debate over planned constitutional amendments already set back by the row.

"Trying to bring down a government and its reforms because one official went out of control?" tweeted LREM spokesman Gabriel Attal.

Macron will be hoping for some respite as MPs head off on their summer break Wednesday.

Confidence votes are fairly common in France: there have been more than 100 since the current constitution was adopted in 1958.

Only once has such a move actually brought down a French government, that of Georges Pompidou in 1962.