A UNITED Nations body has called for the immediate release of four Catalan prisoners, some of whom have been in jail for up to 20 months.

This is the second report from the UK Working Group in Arbitrary Detention (WGAD) – in May it urged the release of Jordi Sànchez and Jordi Cuixart, political activists at the time of the 2017 independence referendum, and former Catalan vice-president Oriol Junqueras.

The group said the detention of former ministers Joaquim Forn, Raül Romeva, Josep Rull and Dolors Bassa, is “arbitrary” and a breach of the Universal Declaration of Human Rights. They are among the 12 Catalan leaders who were tried at Spain’s Supreme Court in the independence trial, and are now waiting for the verdict.

In its 17-page report, the WGAD said the detention of Forn, Rull, Romeva and Bassa was due to their exercising of their rights to “freedom of conscience, opinion, expression, association, meeting and political opinion” – which contravened the Universal Declaration of Human Rights and the Convention, as well as breaching the presumption of their innocence.

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Catalonia’s Foreign Minister, Alfred Bosch, insisted that Spanish authorities “comply with the UN Working Group’s decision by releasing the political prisoners immediately”.

He said: “Rulings by international bodies have to be respected and human rights fulfilled.

“The former members of Catalonia’s Government, who are now included in the ruling, had spent exactly 500 days in preventive detention when the working group issued the statement.

“In the case of both Junqueras and Forn they have been incarcerated for more than 20 months without a condemnatory sentence.”

After the WGAD’s first report, the Spanish Government’s response cast doubt on its “impartiality” and “independence”. The executive, led by Pedro Sanchez, said it was “especially serious” that the report was published “shortly before the case against the defendants is over in the Supreme Court”.

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In a statement, it said: “It is a sad circumstance that could be interpreted as interference in the criminal case underway.”

Carles Puigdemont, the former president who is in exile in Belgium, tweeted: “To have political prisoners detained in abusive conditions, and to have the UN tell you that, is a complete rejection of the narrative that Spain is a model democracy.

“Violating the Universal Declaration of Human Rights is a shame for a country in the European Union.”