PARIS (AFP) - Former president Nicolas Sarkozy has slammed the French government's handling of labour law reforms that have sparked strikes and protests across the country, denouncing its "weakness, cowardice and total loss of authority".

The leader of the opposition said President "Francois Hollande had everything wrong from the start" in his handling of the crisis, which has caused chaos two weeks before the start of the Euro 2016 football tournament.

Hundreds of thousands of people have taken to the streets in demonstrations that have frequently turned violent, while petrol pumps have run dry after a prolonged blockade of refineries and depots by CGT union activists.

Faced with a rebellion within his own Socialist party, Prime Minister Manuel Valls used a special constitutional provision to force the bill through the lower house of parliament without a vote earlier this month.

"Pushing it through by force cuts out debate," said Sarkozy in an interview with magazine Valeurs Actuelles, due to be published on Thursday (June 2).

"If you don't accept the debate of ideas in parliament, then it moves to the streets."

The government says the law, named after Labour Minister Myriam El Khomri, is aimed at reducing stubbornly high unemployment and making France's struggling economy more business friendly.

Key parts of the legislation would let companies set their own working conditions for new employees, allowing managers to cut jobs during hard times and go beyond the 35-hour work week introduced in 2000.

Unions have responded with months of unrest, paralysing the country with transport strikes and fuel shortages that have heaped pressure on the deeply unpopular Socialist government.

"What we see today is a shambles," Sarkozy said, warning of "anarchy" on the streets of France.

"The bill is far too weak to solve the problems, but stinging enough to arouse the passions of the left. The government has proven its weakness faced with the protests.

"Weakness, cowardice, a total loss of authority: this is the spectacle we are witnessing," he said.

To avoid a repeat of the crisis, Sarkozy said protest organisers should be liable for any damage caused during their rallies, and called for anyone convicted of attacking a public official to immediately go to jail for a minimum term.

The government should also take control of petrol depots and refineries, he added.