A French association of Covid-19 victims is filing a legal complaint against Prime Minister Jean Castex for alleged mishandling of the pandemic, its lawyer said.

The coronavirus Victims France association, which has 200 members, accuses the government of "playing it by ear" in its response to the crisis, lawyer Fabrice de Vizio told the AFP news agency.

Castex took over from Edouard Philippe as prime minister in July when the worst of the epidemic so far was over in France. But the past weeks have seen a worrying surge in new cases.

The latest complaint will be filed on Thursday with the Court of the Republic (CJR), the only court in France authorised to deal with cases against government ministers over alleged offences committed in office.

The court has already received more than 90 legal complaints against ministers.

A total of nine targeting Philippe as well as Health Minister Olivier Veran and his predecessor Agnes Buzyn have been declared valid by the court, which has begun investigating them for possible "failure to fight a disaster".

Di Vizio said the complaint against Castex highlighted the association's view that shortcomings had continued after he took over as prime minister from Philippe.

"What is striking since his arrival is that there is no strategy whatsoever of fighting the pandemic," he said, adding that the government was simply "guilt-tripping the population".

Di Vizio cited an absence of screening at airports during the month of July, slowness in introducing saliva tests and the government's decision to delegate the responsibility for Anti-Covid measures to regional prefects.

"This country is being managed, not governed," he said.

Contacted by AFP news agencies, Castex's office had no comment.

In June, Paris prosecutors opened a preliminary investigation for "involuntary manslaughter" and "endangering the lives of others" after receiving dozens of legal complaints over the handling of the pandemic, some targeting retirement homes.

Complaints have continued to flood in, with a total of 170 received by the capital's prosecutors by the end of August.

Meanwhile, on Thursday, some of the country's most powerful labour unions held a strike and protested to denounce coronavirus-related job losses and demand wage increases.

The "national day of inter-professional action" took place across several major cities.

In the northern town of Bethune, workers protested at a Bridgestone tire factory over the company's decision to close the plant and lay off its nearly 900 workers, accusing management of using virus-driven economic concerns as a pretext.

Japan-based Bridgestone has argued the factory was already struggling before the pandemic and was the company's "least-performing" facility in Europe.

Both unions and the French government denounced the closure.