If passed, the law would increase maximum overtime hours, essentially adding an extra work day based on the number of hours that could be tacked on.

Thousands of Hungarians protested in Budapest Saturday against a proposed new labor law that allows employers to ask for up to 400 hours of overtime work per year, a move critics have called the "slave law."

Trade unions members and their supporters marched with banners like "we protest against the slave law" and "force your mother to do overtime." Some trade union members wore yellow jackets inspired by the French protests.

While Hungary's Prime Minister Viktor Orban has built a system critics view as autocratic, he has rarely angered large voter groups at once.

The last move that stirred the populace and forced Orban to backtrack was his planned tax on internet data traffic. He abandoned the plan in late 2014 after tens of thousands marched to protest it.

The labor code change that was submitted to Parliament this week has sparked the biggest street protest in over a year. Potentially, it could add two extra hours to an average workday, adding up to an extra workday per week.

"We are all really upset about the way things are going in this country," Zoltan Laszlo, vice chairman of the Vasas ironworkers union, told Reuters. "This government just makes laws with scant consolation of those affected."

"Our health status is already abysmal. People who make these kinds of laws work against society. We'll show them that we can take our fate into our own hands. We are willing to turn a lot harsher."

According to the bill posted on Parliament's website, employers are guaranteed an extra 250 hours of overtime per worker per year. For others, they would have to seek employees' agreement.

Lajos Kosa, the Fidesz lawmaker who was the original author of the changes, told Parliament that the Hungarian workweek will continue to consist of five eight-hour days as a rule, stressing that employees will get paid for any overtime.