Tens of thousands of French leftists are expected to answer a call by firebrand Jean-Luc Melenchon to throng the streets of Paris on Saturday in protest over President Emmanuel Macron's sweeping reforms of the labour code.
The third in a series of nationwide protests comes a day after Macron signed his signature reforms into law using a fast-tracked procedure that avoided a lengthy parliamentary debate.
The changes to the labour code, which runs to around 3,400 pages in some editions, give small businesses more flexibility to negotiate pay and conditions with their staff, instead of being bound by national agreements.
They also make it easier to lay off employees and cap compensation awards for unfair dismissal while also giving higher payouts to workers made redundant.
Macron argues the changes -- the cornerstone of his programme aimed at boosting entrepreneurship -- will help bring down stubbornly high unemployment of 9.6 percent.
Melenchon's hard left France Unbowed party has accused Macron of unravelling decades of hard-won social gains and called on the French to descend on Paris from across the country to try force him to reverse his "social coup d'etat".
Macron has vowed not to be swayed.
"I believe in democracy but democracy is not the street," he told CNN television last week.
Saturday's protest will test continuing resistance to the measures after two days of union-led demonstrations over the past two weeks, the second of which drew a markedly smaller turnout Thursday.
Addressing reporters at the Elysee Palace after signing five executive orders before television cameras Macron boasted that he had implemented his campaign pledge to shake up labour relations "in record time".
The move to give bosses and workers more freedom to negotiate was "unprecedented" in French post-war history, he proclaimed.
Melenchon, a veteran 66-year-old politician showman who placed fourth in this year's presidential election, cast it as an attack "on the last country in Europe that is holding out on its post-war social gains".
"The battle of France has begun," he declared this week.
- 'Slackers, unite!' -
The measures chip into worker protections that have long been sacrosanct in France, frustrating reform-minded governments whether on the left or the right.
Three months of negotiations with union leaders produced a split between those willing to compromise -- the CFDT and FO -- and those determined to fight the reforms, led by the largest and most militant union, the CGT.
The resistance has, however, been weaker than that faced by Macron's Socialist predecessor Francois Hollande last year over his changes to the labour code, which sparked months of sometimes violent protests.
On Thursday, some 132,000 people demonstrated across France, around half as many as protested a week earlier.
The reform comes as former investment banker Macron's approval ratings plunge, with recent polls showing that only around 40 percent of French voters are satisfied with his performance.
His characterisation of opponents of the labour changes as "slackers" has become a rallying cry, with protesters coining slogans such as "Slackers of the world, unite!"
Philippe Braud, professor emeritus at Paris's Sciences Po university, said he believed popularity was not a concern for Macron.
"He knows he won't be defeated in the street," Braud told AFP.
Macron insists he has a mandate for change after his presidential win in May and his party's thumping parliamentary victory in June.
Public opinion is divided, according to a recent BVA poll, with most respondents saying they think the reform will boost France's competitiveness but fail to improve conditions for workers.
© 2017 AFP