As crowds gathered in cities across France for another day of demonstrations, the CGT labor union called for weekly rolling strikes at the SNCF state rail company from Tuesday night until Friday morning.
Prime Minister Manuel Valls' Socialist administration was expected to survive the confidence vote.
But a series of strikes and waves of street protests that have shown no sign of easing since they began in late March suggest popular discontent over a reform that pollsters say three out of four people oppose is becoming more entrenched.
"It's time to move up a gear," Philippe Martinez, head of the CGT union, said. The main objection to the reform from unions is that it would allow firms to adopt in-house terms on pay and conditions instead of complying with national standards.
The official reason for the rail strike call is a standoff with management over conditions, but its timetable dovetails with the broader protests against government policy.
As crowds gathered in cities across France, government spokesman Stephane Le Foll said there was no question of withdrawing the reform.
But it has left an already deeply unpopular President Francois Hollande, who narrowly survived a rebellion by dissenters in his own party on Wednesday, in an uncomfortable position a year from elections.
The reform is also under fire from a rolling youth protest movement known as Nuit Debout, or 'Night Uprising'.
Since the protests began, several hundred police have been injured in clashes, often with hooded youths hurling stones and petrol bombs. On Thursday, news television channels showed footage of secondary-school pupils blocking schools entrances with garbage bins.
The interior ministry advised motorists to stay away from central Paris ahead of an afternoon march and also reported traffic halted by road blockages in some places.
Paris Mayor Anne Hidalgo, a prominent Socialist, added her voice to the dissenters, declaring on Europe 1 radio: "This law does just nothing for social justice."
Hollande has several other problems piling up.
Media speculation is rife that his youthful economy minister Emmanuel Macron could run for president in the election scheduled for May 2017.
His government has also been caught up in a controversy over sexual harassment in the corridors of power.
After the resignation a politician accused of harassing female colleagues, Finance Minister Michel Sapin, a close Hollande ally, on Wednesday admitted behaving inappropriately toward a female journalist.