French far-left firebrand Jean-Luc Melenchon urged protesters Saturday to take to the streets and mount strikes to force President Emmanuel Macron to withdraw the labour law changes that are key to his business-friendly economic vision.
Speaking to tens of thousands in Paris, Mr Melenchon assailed the president's new labour decrees as a gift to greedy corporations and the financial markets that have both fuelled income inequality.
Mr Macron, for his part, says the decrees are crucial to creating jobs and tackling France's chronic high unemployment.
"The battle isn't over, it is beginning," Mr Melenchon told the crowd packed on to the Place de la Republique in eastern Paris.
Earlier, marchers stretched along Paris boulevards waving French flags, union banners and signs reading "Macron, Resign!"
"It's the street that brought down the kings. It's the street that brought down the Nazis," said Mr Melenchon, who is trying to position himself as France's main opposition figure.
The labour decrees that Mr Macron signed Friday reduce French unions' influence over workplace rules and make it easier for companies to fire workers, but Saturday's demonstration reflected wider frustration with the new French president's leadership.
"Everything that's done in terms of fiscal policies is in favour of the rich, the wealthy and big companies," complained marcher Cedric Moulinier, 26.
"We're asking for things to start going the right way, a more social, humanist and environmentalist way."
Many were angry at a reference Mr Macron made to the "lazy" people who opposed the changes.
While the president has already signed the decrees and they are expected to be ratified by parliament soon, Mr Melenchon still insisted it was not too late to overturn them.
He said he would reach out to unions to join forces against the labour decrees, which he said threaten the French way of life.
"All of Europe is watching us. What is happening is the battle for France," he said.
The crowd, which police estimated at 30,000 and organisers estimated at 150,000, repeatedly broke into chants of "Resistance!" or "Get out!"
The protesters are also angry that Mr Macron used a special procedure allowing the government to change labour law by executive order instead going through a lengthy debate to pass a bill in parliament.
Mr Macron lauded the "unprecedented wave of changes" to France's social model, along with changes to unemployment benefits and a training plan for jobless people that will be set up next year.
While Mr Macron shone at the UN General Assembly in New York last week and has made a strong mark on the international stage, he has struggled with myriad critics at home.
Farmers, riot police and carnival workers have held protests in recent weeks over work policy changes under Mr Macron, and truckers plan road blockades on Monday.
Among Mr Melenchon's suggestions to pressure the government to withdraw the reforms is a "pots and pans party".
"Grab your pots next Saturday to make as much noise as possible," he said. "This is what our message will be: You make our lives miserable. You prevent us from dreaming so we will prevent you from sleeping."