Striking rail workers disrupted services across France in protest at the proposed reforms while students forced the closure of some 200 schools.
Riot police used tear gas against stone-throwing demonstrators in the western cities of Nantes and Rennes, while around 100 people were arrested after clashes in Paris, Toulouse in the southwest and elsewhere.
Official figures said 390,000 people had braved heavy rain to join demonstrations around the country -- twice the crowds that turned out a week ago -- while unions put the figure at 1.2 million.
Adding to the president's miserable week, dozens of flights were cancelled due to a separate strike by air traffic controllers.
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The Socialist government is desperate to push through reforms to France's controversial labour laws, billed as a last-gasp attempt to boost the flailing economy before next year's presidential election.
But it has faced a wave of often violent protests by unions and students angry over plans to make it easier for struggling companies to fire workers, even though the reforms have already been diluted once in a bid to placate critics.
The measure had been derided as ineffective and divisive, including by leftwing rebels within the Socialist party, but Hollande's critics accused him of yet another humiliating climbdown.
Already the least popular president in France's modern history, Hollande's numbers continue to fall, with a poll today showing his approval rating at a new low of 15 per cent.