The centrist party of French President Emmanuel Macron was left red-faced on Tuesday after opposition parties joined forces to hold up a bill tightening measures against Covid-19.

The lower house National Assembly was debating the implementation of a health pass that will require a full course of vaccination to attend events, eat out or travel by inter-city train, rather than a recent negative test or proof of recovery.

But when the government asked the chamber late Monday to continue debating the legislation after midnight, to ensure it could be adopted by the end of the week, the right-wing Republicans (LR) teamed up with the far-right and far-left to stop the debate.

In an embarrassment for Macron's Republic on the Move (LREM) party that controls parliament, not enough of its lawmakers were still present in the chamber when the vote by a show of hands was taken on continuing the debate.

French media said the surprise move by the LR -- which has backed the main thrust of the legislation -- pointed to rising political tensions ahead of April 2022 presidential elections, which Macron appears the favourite, but is not certain, to win.

Government spokesman Gabriel Attal lashed out at a "procedural coup" by opposition lawmakers, saying they wanted to "derail the calendar" for the vaccine pass for purely political reasons.

"We will do everything to stick to the calendar as has been set out," he told France Inter radio. The government wants the new legislation to be implemented from January 15.

The debate was due to resume late Tuesday, parliamentary sources said, with 500 amendments filed by the opposition to be discussed and lawmakers facing another late night.

'Always an amateur' 

The delay underscored the frailties of LREM, an upstart centrist party that has failed to build up a solid base since Macron's meteoric rise to the presidency in 2017.

"Once an amateur, always an amateur," commented Damien Abad, head of the LR faction in the National Assembly, describing the vote as a "big blow for the ruling party and the government".

Prime Minister Jean Castex told a meeting of LREM lawmakers that the events of Monday night "did not match the gravity of the situation" and that the party now needed to be "more united than ever", according to participants.

After a bitter New Year's debate over a move to fly the European flag from the Arc de Triomphe monument to mark France's turn at the EU presidency, Le Monde daily said the episode was a new sign of pre-election tensions.

"The presidential election campaign appears to have barged into the debates on health policy," it said.

Valerie Pecresse, the LR candidate considered the main threat to Macron by analysts, confirmed Tuesday that her party would back the legislation.

She warned however that it would be modified when it arrives in the Senate, where the right holds a majority, and criticised a "lack of preparedness and improvisation of the government in the face of the crisis".