Thousands of Hungarians have protested in Budapest against the government’s new labour law as left-wing anger grows over the authoritarian rule of right-wing nationalist prime minister, Viktor Orban.

Sunday’s protest, billed as the “Merry Xmas Mr Prime Minister” march by organisers, was the fourth day of demonstrations in the past week by leftist opposition parties, student groups and civilians campaigning against Mr Orban’s government.

The new law allows employers to ask for up to 400 hours of overtime work per year, leading critics to label it the “slave law”.

Mr Orban’s government has also faced criticism over a recently-passed law allowing the government to establish new administrative courts. The courts will oversee sensitive issues such as electoral law, protests and corruption issues.

Activists waved both Hungarian and EU flags as they marched from Heroes’ Square towards parliament.

“Discontent is growing,” said Andi, 26, a sociology student who attended Sunday’s march. “They have passed two laws this week which ... won’t serve Hungarian people’s interest.”

Mr Orban has repeatedly clashed with EU leaders in Brussels after boosting his control over the courts and the media.

Civil rights watchdogs said the new court law was the latest erosion of democratic institutions under the country’s prime minister, who came to power in 2010.

He has since tweaked the election system to favour his ruling Fidesz party and has put loyalists at the head of public institutions.

Protest against the government in Hungary: in pictures Show all 12 1 /12 Protest against the government in Hungary: in pictures Protest against the government in Hungary: in pictures Anna Donath, Vice President of opposition party Momentum Movement holds a flare during the protest Reuters Protest against the government in Hungary: in pictures A protester kneels in front of riot police outside the headquarters of Hungarian state television AFP/Getty Protest against the government in Hungary: in pictures Protesters hold up their phone lights outside the Hungarian parliament Getty Protest against the government in Hungary: in pictures Protesters march across the Margaret Bridge on the Danube n downtown Budapest EPA Protest against the government in Hungary: in pictures Protesters stand outside the Hungarian parliament building Reuters Protest against the government in Hungary: in pictures Police stand guard in front of the headquarters of Hungarian state television AFP/Getty Protest against the government in Hungary: in pictures Protesters line the streets by the Hungarian parliament building Getty Protest against the government in Hungary: in pictures Protesters march across the Margaret Bridge on the Danube in downtown Budapest EPA Protest against the government in Hungary: in pictures A protester lights a flare in protests against the Hungarian government Reuters Protest against the government in Hungary: in pictures Police forces secure the area outside the headquarters of Hungarian state television Reuters Protest against the government in Hungary: in pictures Protesters hold up their phone lights outside the Hungarian parliament Getty Protest against the government in Hungary: in pictures Protesters wave a flag outside the Hungarian parliament Reuters

He has rarely angered large voter groups, but street demonstrations organised by left-wing groups began in the capital earlier this week. On Thursday police used tear gas on protesters outside the parliament building.

Mr Orban was re-elected in April on the back of a fiercely anti-immigration campaign, facing a weak and fragmented opposition.

Earlier this month, his government forced the Central European University to leave Hungary as part of Mr Orban’s long-running campaign against its founder, the Hungarian-born billionaire George Soros.

Fidesz released a statement on Saturday claiming it was “increasingly obvious that criminals have been part of the street riots organised by the Soros-network".