SENIOR figures on both sides of the Scottish independence divide have accused the Spanish state of "oppressing Catalan democracy".

A leading playwright, a human rights lawyer and Scotland's biggest public sector union are among the signatories of an open letter savaging Madrid for its "authoritarian actions" and calling for all of Scotland's civic institutions to show "solidarity" with Catalan dissidents.

In an unprecedented condemnation of the Spanish government, figures from Scottish civic society say that "police violence must not be used against innocent civilians simply exercising their rights".

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The demand was a reference to the behaviour of Spanish state forces in last October's Catalan independence referendum. Spain was later criticised by Amnesty International for using "disproportionate force" and injuring hundreds of civilians as they tried to vote.

In a highly significant call, the campaigners say that “Catalan leaders forced into exile must not be extradited to Spain”.

Public sector union Unison Scotland – Labour’s second biggest union - is one of the most high profile signatories from outside the independence movement. Other Labour backers include the party's former Scottish chair, Bob Thomson.

Glasgow trades council - the body representing trade unions in the city - has also signed the letter, alongside playwright and novelist Alan Bissett, human rights lawyer Debora Kayembe, Scottish Greens co-convenor Maggie Chapman and SNP MSP Sandra White.

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SNP MP Chris Stephens and writer and broadcaster Lesley Riddoch are also among more than 20 signatories to the open letter.

It says: "We must recognise the fundamental and inalienable rights of all peoples across the world to self-determination and condemn in the strongest possible terms the authoritarian actions of the Spanish state in oppressing Catalan democracy.

"Many of the rights we enjoy today were secured through the collective solidarity of people and organisations across the world. We offer that solidarity today and tomorrow.

"We are calling on Scotland’s people, political parties and civic institutions to show that same solidarity. Not to reflect their support for independence, to protect the principles of democracy against authoritarianism.

"With arrest warrants executed in Scotland and elsewhere in Europe, the protection of human rights is firmly in the hands of civic society across the continent."

The condemnation comes as legal proceedings intensified against former Catalan minister Clara Ponsati, who will face a two-week hearing in July on whether she will be extradited from Scotland to Spain on charges of rebellion.

The letter calls for an end to the use of European arrest warrants against figures such as Ponsati, who is one of five former ministers Spain’s supreme court wants to extradite.

"Catalan leaders forced into exile must not be extradited to Spain, where we question whether they would receive a fair trial given the ongoing criminalisation of dissent," the letter states.

"Police violence must not be used against innocent civilians simply exercising their rights. The rights that underpin our society must not be trampled on. The time for action is now."

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Jonathon Shafi, an organiser with the Catalan Defence Committee Scotland, which was set up last year, welcomed the intervention.

He said: "This letter is not about independence but about democratic rights.

"Last year we saw batons come down on proactive citizens exercising their right to vote. This has set a precedent in Europe.

"The repression continues in various forms today, including, of course, through the incarceration of Catalan activists and leaders.

"European leaders cannot wish this problem away. Action is required to safeguard civil liberties not just in Catalonia but across the continent."