A 37-page document sent this week accused the Spanish government of “criminalising” the independence movement by initiating a “repressive crackdown” that has led to the imprisoning of former ministers.

It comes after Puigdemont announced on Thursday that he was abandoning his attempt to return as Catalan president and would throw his weight behind Jordi Sànchez, an MP in his Together for Catalonia party and the former leader of the grassroots Catalan National Assembly (ANC).

The complaint to the UN is part of a series of legal initiatives by the pro-independence campaign aimed at embarrassing Spain in international tribunals.

The papers, signed by Puigdemont, also alleged that his right to freedom of association and assembly, as well as freedom of opinion and expression, have been illegally suppressed, thereby breaching the universal declaration of human rights and the international covenant on civil and political rights.

“The series of steps taken by the Spanish executive and judicial authorities has rendered it impossible for him to discharge his duties and responsibilities as the democratically elected president of Catalonia,” the submission argued.

“The applicant’s right to participate in the government of his country through democratic elections has been snuffed out and the right of the people of Catalonia to elect their chosen representatives to govern them has been frustrated by repressive actions of the central authorities in Madrid.

“As a consequence, the applicant has been forced against his will and under protest to step aside to allow the nomination of an alternative candidate. He takes this step in the interests of the Catalan people, to enable the Catalan parliament to perform its governing function, to re-establish a measure of autonomy for the region, and thereby to advance Catalonia along its journey towards independence.”

Sànchez has been in prison since mid-October, when he and another pro-independence civil society group leader, Jordi Cuixart, were arrested as part of an investigation into alleged sedition in the run-up to the independence referendum.

It is unclear whether Sànchez would be allowed out of prison to be invested or whether he commands the support of the two other pro-independence Catalan parties.

The proposal was swiftly dismissed by the Spanish prime minister, Mariano Rajoy, who has called on the Catalan parliament to choose a “clean” candidate.

“I ask that they choose a president who doesn’t have legal problems,” Rajoy said in an interview with the broadcaster Telecinco.

“Anything else is frankly a joke. As far as I’m concerned, they can choose whoever they want, but I think choosing someone with legal problems would be an enormous mistake and would send the message ‘We’re carrying on with the confrontation’.”

The document sent to the UN said Puigdemont remains willing “to enter into political dialogue” with Madrid “on behalf of the Catalan people” as a means of securing the release of “political prisoners”.

As well as Sànchez and Cuixart, the former Catalan vice-president Oriol Junqueras and the former Catalan interior minister Joaquim Forn remain in prison facing possible charges of rebellion and sedition.

“The Spanish government’s attempt to criminalise the independence movement was a turning point,” the submission said.

“It marked the hardening of its political strategy and the start of a repressive crackdown that was to involve all organs of state power, including the national legislative, executive and judicial authorities, and the monarchy itself.”

Lawyers for Sànchez, Cuixart and Junqueras have lodged an application with the UN working group on arbitrary detention.

The court, the submission noted, has indicated that the trials of those charged with rebellion and sedition would not conclude before December, by which time the four men “being arbitrarily deprived of their liberty for the exercise of their political rights” will have been in prison without trial for more than a year.

In a briefing in Brussels on the legal situation, Ben Emmerson QC, representing Puigdemont, said: “When one considers the sequence of events that has generated the current crisis in Catalonia, it is self-evident that all organs of the Spanish state have been mobilised in a concerted and cumulative attempt to squeeze the life out of the Catalan independence movement.

“Spain is holding a sword of Damocles over the head of the Catalan people, implementing a strategy that is designed to cower them into submission.”

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