Hundreds of thousands of people are expected to take to the streets across France on Tuesday
Hundreds of thousands of people are expected to take to the streets across France on Tuesday AFP

France's left-wing forces and labour unions will stage another day of strikes on Tuesday to try to derail President Emmanuel Macron's pensions overhaul, insisting that the fight to thwart the changes is not over even after it became law.

Hundreds of thousands of people are expected to take to the streets across France for what will be the fourteenth day of demonstrations since January to oppose the reform.

Macron signed in April the bill to raise the pension age to 64 from 62 after the government used a controversial but legal mechanism to avoid a vote in parliament that it risked losing.

The later retirement age, which seeks to bolster France's troubled long-term finances, was a banner pledge of Macron's second and final term in office, and its smooth implementation is seen by supporters as crucial to his legacy.

Parts of the overhaul, including the key increase in the pension age, were printed Sunday in France's official journal, meaning they are now law.

Opponents are pinning their hopes on a motion put forward by the small Liot faction in parliament -- broadly backed by the left -- to repeal the law and the increased retirement age.

Parliament speaker Yael Braun-Pivet, a member of Macron's party but officially neutral, was to rule on Thursday whether parliament could vote on returning the retirement age to 62.

This was removed from the Liot motion at commission level, but left-wing parties have sought to put it back on the agenda via an amendment.

In an op-ed for the Le Monde daily on Monday, the key figures from all of France's left-wing parties urged Braun-Pivet to allow a vote on the motion, at the risk of further unrest.

"For our fellow citizens, a new denial of democracy will only lead to increased disaffection for our institutions, which is already manifesting itself in the form of growing abstentionism, and even an increase in anger and violence," they said.

Authorities expect up to 600,000 people at the demonstrations nationwide Tuesday, less than half the peak on March 7, when 1.28 million were counted by police.

In contrast to the earlier phase of the movement, only limited disruption is expected on public transport though some flight cancellations are awaited, in particular at the Paris Orly airport.

"The defeat has not been enacted," Greens MP Sandrine Rousseau told Radio J, warning that "we will raise our voices" if the parliament vote is not allowed.

The battle against the pensions reform "will never finish", hard-left leader Jean-Luc Melenchon told the 20 Minutes daily.

But Macron's allies say it has long been game over for opponents of the reform, even if it remains widely unpopular with the public.

The opposition "knows very well that this motion has no future," Prisca Thevenot, an MP for Macron's Renaissance party, told LCI television on Sunday.

The government says the changes are essential for France's financial health.

In April, Fitch, one of the leading credit ratings agencies, lowered its rating on France's debt, which is approaching three trillion euros ($3.2 trillion).

But France managed to avoid a new credit downgrade on Friday, when S&P Global maintained the agency's "AA" rating.