About 170,000 took to the streets, a day after Prime Minister Pedro Sanchez was sworn in for a second term.

Sanchez’s Spanish Socialist Workers’ Party (PSOE) secured the backing of the Catalan separatist Junts party by offering amnesty to those linked to a botched bid for regional independence six years ago.

According to the authorities, more than 170,000 took part in Saturday’s protest, the largest yet against the deal, which has prompted the opposition to take to the streets in cities across the country.

Sanchez was sworn in on Friday, nearly four months after an inconclusive election left the country with a hung parliament. The conservative main opposition People’s Party (PP) won the largest share of the vote, however, the right-wing coalition with the far-right Vox party failed to secure the absolute majority needed to form a government.

Protesters waved Spanish flags and held signs that read “Sanchez traitor” and “Don’t sell Spain”.

Four judicial associations, opposition political parties and business leaders say the law threatens the rule of law and the separation of powers.

PP leader Alberto Nunez Feijoo and Santiago Abascal, head of Vox, were among the demonstrators.

After the rally, hundreds of people protested on the motorway near the Moncloa Palace, the prime minister’s residence in Madrid. The A6 road was closed for about an hour during the protest but later reopened after the police cleared the area.

A small protest was held outside the Spanish Embassy in London.

Approximately 400 people involved in the independence bid that came to a head in 2017 will benefit from the law, including both separatists and police involved in clashes with activists.

Among them is former Catalan President Carles Puigdemont, the leader of Junts and the brains behind the illegal referendum, who today lives in exile in Belgium.

The independence referendum was declared illegal by the courts and resulted in Spain’s worst political crisis for decades.

The amnesty will be the largest in Spain since the 1977 blanket amnesty for crimes committed during the Francisco Franco dictatorship, and the first amnesty law approved in the European Union since 1991, according to Spain’s CSIC research council.

Sanchez, who won a parliamentary vote to form a new government on Thursday by 179 votes in favour and 171 against, has defended the law saying an amnesty would help to defuse tensions in Catalonia. Some of his ministers, including PSOE senior official Felix Bolanos, have hailed the legislation as a way to “heal wounds and resolve the existing political conflict” in the region.

Protesters, including neo-Nazi groups, have held demonstrations outside the Socialist party’s headquarters in Madrid for 15 consecutive nights since the deal was announced, leading to violent clashes with police and arrests.

In a survey by pollster Metroscopia in mid-September, approximately 70 percent of respondents – 59 percent of them Socialist supporters – said they were against the idea of an amnesty.