A RARE agreement between Catalonia and Spain to have an impartial observer present during talks aimed at solving the political crisis there has been criticised by the main Catalan unionist party.

At the heart of yesterday’s agreement are the fears of Spanish prime minister Pedro Sanchez that his budget proposals might not make it through parliament without the support of the Republican Left of Catalonia (ERC) and other pro-Catalan independence parties.

They helped his Socialist party (PSOE) oust Mariano Rajoy, but he needs their continued support to pass legislation.

Sanchez has repeatedly told Catalan leaders he would not discuss self-determination, so his acceptance of a “neutral observer” at talks with Catalan government leaders took some by surprise.

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The unionists Ciutadans (Citizens) party called it “a humiliation and a disgrace” for Spain.

Party leader, Albert Rivera, said: “We don’t accept that those who have carried out a coup should set conditions on those who respect the rule of law.”

Citizens yesterday asked for Sanchez to appear before Congress to explain the move, because it said he had “sold the national sovereignty”. Inés Arrimadas, Ciutadans’ leader in Catalonia, said it showed Sanchez’s “desperation” to retain power.

Pablo Casado, leader of the People’s party (PP), said Sánchez was committing “high treason”, and added: “We will activate the necessary measures to curb the high treason of Sánchez to Spain.

“His surrender to independence is the most serious felony since the 23F [the attempted coup in February 1981]. He’s delegitimised to stay in government.”

In a tweet yesterday, Casado did not rule out tabling a motion of no confidence against the Socialists.

However, the left-wing Podemos party welcomed the observer as “a tool to build bridges and facilitate dialogue”.

Its spokesperson in Congress, Irene Montero, said: “I do not think that an observer or a mediator at a negotiating table will put democracy at risk.”