LONDON — Viktor Orban, the far-right prime minister of Hungary, has been confronted by an unusually persistent wave of street protests after pushing through a bill this month that could require workers to put in up to 400 hours of overtime — a measure that opponents call a “slave law.”

About 5,000 demonstrators took to the streets of Budapest again on Friday, after President Janos Ader signed the bill into law. In a radio interview Friday morning, Mr. Orban dismissed opposition to the changes as “hysterical shouting.”

Since re-entering office in 2010, Mr. Orban has made a series of moves that have set off alarms among European allies and others in Hungary: curbing judicial independence, restricting news media freedom and plurality, and blatantly enriching his business allies. But few of his actions have ignited such anger as the changes to the labor law.

What does the law say?

The amendments to the Hungarian labor code passed by the governing majority in Parliament raise the yearly cap on overtime to 400 hours from 250, and gives companies three years instead of one to pay for the work.