PARIS (Reuters) - French far-left opposition party leader Jean-Luc Melenchon drew tens of thousands to a rally on Saturday against President Emmanuel Macron’s labor reforms, aiming to reinforce his credentials as Macron’s strongest political opponent.

Far-left opposition "France Insoumise" (France Unbowed) party's leader Jean-Luc Melenchon delivers a speech at the end of a demonstration against the government's labour reforms in Paris, France, September 23, 2017. REUTERS/Philippe Wojazer

Trade union protests against Macron’s plan to make hiring and firing easier and give companies more power over working conditions seem to be losing steam, but Melenchon said his “France Unbowed” party was calling on unions to join them and together “keep up the fight”.

“The battle is not over, it is only starting,” Melenchon told the crowd gathered on the Place de la Republique where the rally against what Melenchon has called “a social coup d’etat” ended.

In a warning to Macron, who has said he will not bow to street pressure, Melenchon said: “It is the street that defeated the kings, it is the street that defeated the Nazis,” while the crowd chanted “Resistance! Resistance!”

It remains to be seen whether Melenchon and his party have the capacity to mobilize the kind of street resistance which forced the last two presidents to dilute their own attempts to loosen the labor code.

Melenchon tweeted that over 150,000 demonstrators had turned up while police put the number at 30,000.

A campaign rally in March, weeks before the presidential election, drew some 130,000 people, party officials had said.

“Today we are sending an extraordinary strong message to the workers that they are not alone,” Melenchon added.

Macron campaigned for the presidency as someone who could bridge the divide between left and right.

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But since his election, he has already alienated many, especially on the left, by saying he would be a “Jupiter-like” president, above the fray, and with his avowed determination not to tolerate “slackers”.

Some of Saturday’s protesters carried banners reading “The slackers are in the streets” or “Macron president of the wealthy”. Party officials said about 150 buses had brought protesters from all over France.

Brigitte Gerard, a 59-year-old school teacher from Rennes, in western France, carried a banner reading: “Watch out Jupiter, the people are rumbling”.

“There is a lot of anger,” she said as the march set off for the Place de la Republique. “I don’t think they’re aware of it. They’re cut off from reality.”

“ARM-WRESTLING CONTEST”

The new labor rules, discussed at length in advance with unions, will among other measures cap payouts on dismissals that are judged unfair.

“Emmanuel Macron has started an arm-wrestling contest with the French people ... but I think we can stop these decrees,” France Unbowed lawmaker Adrien Quatennens told Reuters.

A string of opinion polls showing the far-left maverick Melenchon as the strongest opponent to Macron’s upstart En Marche (On The Move) party, highlight the weakness of the traditional mainstream parties.

The Socialists, who ruled from 2012 to 2017, are in tatters, the conservative Republicans are divided over whether to back Macron, and the far-right National Front, whose leader Marine Le Pen reached the second round run-off against Macron, is weakened by internal fighting.

Ironically, Melenchon’s strength could be a good thing for Macron, because polls also indicate that he is not seen as a credible alternative but rather as a conduit for protest.

In an Odoxa survey carried out this week, 66 percent of respondents said Melenchon would be a bad president.

The centrist president formally signed the labor decrees on Friday, and they are due to enter into force by the start of next year.

The measures are only the first step of a series of reforms that will also amend the unemployment benefit and pension systems, changes that could well provoke more protests than changes to the labor code.