Opposition outrage at Sánchez plan to pardon jailed Catalans

However, opposition parties have threatened to launch legal challenges in Spain and Europe against any such government pardons.

"The spirit of the Spanish constitution includes both punishment and concord. There is a time for punishment and a time for concord," Sánchez said during a parliamentary debate this week, triggering accusations of "betrayal" and "humiliation" from right-wing lawmakers.

The opposition centre-right Popular Party (PP) announced on Thursday (28 May) the a parliamentary battle of "institutional pressure" against such a move by, for example, seeking the opinion of all local authorities.

The conservative party also warned that it will appeal against granting pardons at the Supreme Court, as has far-right Vox party. But it is still unclear whether they will be able to do so, as they are not part of the pardon process.

Both parties argue that such a decision would put into question the ruling of Spain's top court from 2019.

"We will oppose pardons with all the instruments at our disposal," PP lawmaker Teodoro García said on Thursday.

For its part, Vox said it will organise street protests if Sánchez pardons the separatist figures.

Meanwhile, the Supreme Court has also positioned itself against either a "total or partial" pardon to the Catalan leaders.

They argue that "there is not the slightest evidence or faintest hint of contrition" - a key requirement for granting a pardon, which can only be issued by the government.

The court also said that it had applied "the principle of proportionality" in its sentencing of the Catalan leaders, nine of whom are serving between nine to 13 years in prison.

Amnesty vs pardon

This non-binding report of the Supreme Court has provided legal ammunition for the opposition parties - amid a resurgent rightwing which now see its position further legitimised.

"This is an issue that could make prime minister Sánchez lose power," former member of the Spanish judiciary council and Catalan lawmaker Alfons López Tena told EUobserver.

"Most Spaniards, [a] part of the socialist governing party, and the right-wing and far-right opposition parties are against pardons to people who say they are willing to commit the same crimes again," he said, pointing out that Spain's top court could annul the pardons for "arbitrariness".

A pardon has been discussed by the government for months, but it picked up speed this week - when Catalonia's newly-elected leader, leftwing Pere Aragonès, took office, pledging to work toward full "amnesty" for the jailed leaders and the self-determination right of Catalonia.

For López Tena, pardons are unlikely to improve relationships between Madrid and Barcelona.

"If they get the pardons, they will show reluctance and mobilise for amnesty," he said.

Amnesty, unlike pardon, would also affect the Catalan leaders who fled to Belgium and Scotland after heading the failed secession attempt - namely former regional premier Carles Puigdemont, and two members of his government.

A final decision is expected over the summer.

Only six of the 137 pardons granted by the Spanish government in the past five years were approved after a negative such report from the court.

Sánchez's coalition government was only possible due to the abstention or support of pro-independence Catalan parties.