PARIS — Firing an employee in France often means a court date, months of hearings and hefty payouts under the country’s 3,400-page labor code. Employers hate the thick book.

But workers — those lucky enough to have jobs — love it. On Wednesday, thousands went into the streets across France to protect it, demonstrating against a new government plan to make firings slightly easier and France’s trademark shortened workweek slightly longer.

Nothing for years has so revived labor tensions — or divided the Socialist Party — as the government’s plan to overhaul the voluminous labor code, removing, ever so slightly, a few layers of worker protection.

Desperate to reduce a nearly permanent unemployment rate of more than 10 percent, the Socialist prime minister, Manuel Valls, has risked taking a delicate paring knife to the labor code, a step that members of his party consider a heresy.