In a major overhaul of its pension scheme, the French government has proposed that people work two years longer to get a full pension, drawing a hostile response from trade unions who said they would step up strike action to force an about-face.

The reform-minded CFDT had stayed out of the strike, which has caused travel chaos across the country since December 5. But it said a "red line" had been crossed and called on members to join mass protests on Tuesday.

"Let's be clear: CFDT railway workers do not want a blockage during the holidays. Then in January (...) if the text has not changed, the CFDT will continue to mobilise," CFDT Secretary General Laurent Berger told Journal du Dimanche.

"We should not make users pay the bill. It would be unbearable if they could not spend this holiday season with their loved ones. We have to break the deadlock," he also said.

In contrast, hardline CGT union on Thursday had warned that there would be no break for Christmas unless the government dropped the whole pension reform plan.

Prime Minister Edouard Philippe told Le Parisien Dimanche he would meet unions next week and asked everyone to take responsibility ahead of Christmas.

"I don't think the French would accept that some people could deprive them of this moment," Philippe said.

French retailers and hoteliers have warned that their crucial Christmas season could be derailed if the transport strike drags on for much longer.

Australian Associated Press