On December 12, Hungary’s parliament passed a law allowing employers to demand staff work up to 400 hours overtime per year, with payment delayed for up to three years. The measure advanced by far-right Prime Minister Viktor Orbán’s Fidesz government sparked mass protests without precedent since he came to office in 2010.

Widely derided as a “slave law,” the move could force Hungarians to work an extra day a week, with the much-delayed payment likely eroded by inflation. The means of the bill’s passing — rammed through parliament by an authoritarian government regardless of constitutional niceties — has linked it to a wider battle over Hungarian democracy.

Over the last week rallies have spread across the country. The largest thus far was in a freezing Budapest on Sunday, as 15,000 demonstrated, but after a series of other protests and blockades unions are talking of calling a general strike in January. Led by unions and students, the movement also includes the whole sweep of parties opposed to Orbán’s government.