French President Emmanuel Macron believes reforms will allow flexibility and create more jobs, while the protesters say they threaten labour rights.
President Emmanuel Macron faced the first challenge on the streets to his business-friendly reform agenda on Tuesday when workers from the hard-left CGT union began marching through French cities to protest against a loosening of labour laws.
After weeks of negotiations, the government last month revealed measures including a cap on payouts for dismissals adjudged unfair and greater freedom for companies to hire and fire and to set pay and working conditions. It plans to adopt the new decrees on September 22.
Protesters argue reforms will give more power to companies when it comes to negotiating salaries, and limit the damages paid to workers who have been unfairly dismissed.
Sounding a call to the working class, Philippe Martinez, the head of the Communist Party-linked CGT, branded the reforms a "social coup d'etat" and took offence at Macron's pledge to give no ground to "slackers".
TRT World's Europe correspondent Simon McGregor-Wood reports from Paris.
French far-left politician Jean-Luc Melenchon joined protesters marching in Marseille.
Thousands took to the streets in the southern port city in the CGT demonstration. The union said 60,000 people participated. Police said the figure stood at 7,500.
In central Paris, riot police clashed with hooded youths on the fringe of a protest.
Police fired water canons and could be seen dragging several demonstrators behind their lines, Reuters TV images showed.
Labour unions have scuppered previous attempts to weaken France's labour code, but this time there was comfort for Macron as two other unions, including the largest, the CFDT, declined to join the protests.
"I am fully determined and I won't cede any ground, not to slackers, nor cynics, nor hardliners," Macron told French business leaders on Friday during a trip to Athens.
Rights vs jobs
French workers have long cherished a strict labour code protecting their rights. But companies complain it has deterred investment and job creation and stymied economic growth.
The reforms are being closely watched in Germany. The changes to the code are seen as a test of the French leader's resolve to reshape the euro zone's second-biggest economy, a must if he is to win Berlin's backing for broader reforms to the currency union.
Martinez called Macron's talk of slackers "scandalous" and said public discontent was rising.
Macron, asked on Monday if he regretted his choice of words, fired back: "We cannot move forwards if we don't say things as they are."
For decades, governments on the political left and right have tried to overhaul the 3,000-page labour code, but ended up watering down their plans in the face of street demonstrations.
Macron was economy minister in the socialist government of former president Francois Hollande, whose attempt at labour reform – dubbed the El Khomri law – led to weeks of protests and stoked a damaging rebellion within his own ruling party.
An opinion poll published on September 1 showed voters have mixed views on the reform. Nearly six in every 10 people oppose Macron's labour decrees overall, but when they look at specific measures they approve most of them.
With economic growth accelerating, unemployment on a downward trend and the country's leading unions divided in their response to the reforms, it is not clear whether the protests will gain momentum.
French voters "chose Macron to carry out the reforms which France have shrunk away from for 30 years," Finance Minister Bruno Le Maire told the newspaper Les Echos.
While the moderate CFDT described Macron's labour decrees as a "deep disappointment" it has said it will not join the CGT demonstrations.
Neither will the smaller Force Ouvriere (FO), usually an ally of the CGT; a decision that has led to discord within the FO's ranks with some factions saying they would join the protests.
"We took part in the protests against the El Khomri law. These decrees are El Khomri plus plus," Patrice Clos, head of one federation within the FO, said. "We can't accept something that we were against a year ago."