France's trade unions on Wednesday defended their decision to cut power to thousands of homes, companies and even the Bank of France to force the government to drop a wide-ranging pension reform.

The power cuts, illegal under French law, added to a sense of chaos in the second week of nationwide strikes that have crippled transport, shut schools and brought more than half a million people onto the street against President Emmanuel Macron's reform.

Asked on French radio whether the power cuts weren't a step too far, Philippe Martinez, the head of the hardline CGT union, said the cuts were necessary to force Macron to back down.

"I understand these workers' anger," the mustachioed union leader said. "These are targeted cuts. You'll understand that spitting on the public service can make some of us angry."

Following a meeting with government officials, he hinted at further cuts, saying "we may amplify these kinds of methods".

Martinez' remarks coincided with comments by Macron's office saying the president ruled out abandoning his reform plans but was keen to make improvements in talks with unions, ahead of a new day of talks between his prime minister and union leaders.

The government is keen to reach a truce before Christmas, when millions of French people travel to spend the holiday with their families.

Macron's transport minister condemned the power cuts, which hit at least 150,000 homes on Tuesday according to power grid operator RTE, and said the government would ask RTE to file complaints.

"Cutting power to ...companies, prefectures, shopping malls, that's already rather questionable," Elisabeth Borne said.

"But clinics, metro stations, fire brigades and thousands of French people also saw power cuts. This is far from normal ways of striking," she added.

Macron wants to turn the myriad of French pension systems into a single points-based one.

That would force staff at state-owned firms such as railway SNCF or utility EDF, who enjoy more generous pension plans than private-sector workers, to work longer.

SNCF train drivers can retire at just over 50, for instance, against 62 for those in the private sector. That means taxpayers have to plug the SNCF pensions deficit to the tune of 3 billion euros every year.

Martinez said that rather than reducing the pension system's deficit by increasing the retirement age, the government should increase corporate social security contributions, tax financial products and make internet firms pay social security charges.

The government argues that increasing pensions contributions would make labour more costly and force young people to pay yet more to fund French pensions.