French Prime Minister Elisabeth Borne will trigger a special constitutional procedure to push an unpopular pension reform bill through the National Assembly without a vote, the Elysee said on Thursday.

The move, using the so-called article 49.3 of the constitution, will ensure the bill raising the retirement age by two years to 64 is adopted, but it shows President Emmanuel Macron and his government failed to garner enough of a majority in parliament.

Resorting to the measure is likely to further enrage unions, protesters and left-wing opposition parties that say the pension overhaul is unfair and unnecessary.

"This government is not worthy of our Fifth Republic, of French democracy. Until the very end, parliament has been ridiculed, humiliated," Fabien Roussel, head of the French Communist Party said.

Socialist Party head Olivier Faure told Reuters earlier on Thursday that such a move could unleash "an uncontrollable anger" after weeks of rolling strikes and protests.

Opposition parties are likely to request a vote of no confidence in the government, however that is unlikely to pass as most conservative lawmakers would likely back the government.

Borne was greeted by boos as she arrived in the National Assembly to announce the special procedure. The session was suspended for two minutes after left-wing lawmakers singing the national anthem prevented Borne from speaking.

Some brandished placards reading "No to 64 years."

Macron and his government say raising the retirement age is necessary to get the pension system out of the red by the end of the decade.

His failure to get the pension overhaul passed by a majority in parliament is not only a serious blow to his reformist credentials, but it risks destroying much of his political capital for the rest of his second mandate, which runs until 2027.