PARIS: French unions have called on workers to walk off the job and join protest rallies on Thursday for a twelfth nationwide day of protests against a bill that will make the French work longer.

Some trains will be cancelled, and strike actions can also be expected among refinery workers, garbage collectors and teachers, at a time when opinion polls show a wide majority of voters still oppose pushing retirement age by two years to 64.

But industrial action has lost steam, and the latest rallies have gathered fewer people than the record crowds seen earlier this year that brought millions of protesters out on the streets.

This newest wave of protests takes place a day before Friday's much-awaited verdict by the Constitutional Council on the legality of the bill.

If the Council gives its green light, even with some caveats, the government will be entitled to officially promulgate the law, and will hope this will eventually put an end to protests, which have at times turned violent, and coalesced widespread anger against Macron.

The French president told a news conference on Wednesday that he would organise a meeting with unions after the Council's decision, to start working on other proposals.

"The country must continue to move forward, work, and face the challenges that await us," he said during a state visit to the Netherlands.

The level of opposition to the policy changes could in any case have longer term repercussions - one question being whether widespread disillusionment with politics could boost the far-right.

"I'm not that optimistic about the Constitutional Council's decision," far-right leader Marine Le Pen told BFM TV, who is against the pension bill. "But what do you want me to do? Burn cars? We'll just tell the French: Vote for the National Rally."

Macron and his government argue the law is essential to ensure that France's generous pension system does not go bust.

Unions say this can be done by other means, including taxing the rich more, or making deeper changes to the pension system.

The Gonfreville refinery in northern France run by TotalEnergies started returning to operation on Tuesday, the company said, marking the last of its four domestic refineries to restart after a month-long strike.

However, the CGT union called for a walkout at all refineries on Thursday as part of the nationwide strike.