Catalonia prepares for rule by Skype

They said he would do it "due to legal imperative".

"I promise to act with complete fidelity to the will of the people of Catalonia," Puigdemont, whose JxCat party came second in regional elections in December, added.

The statement of intent came after the Catalan parliament's own lawyers said on Tuesday that a videolink investiture would have no legal basis.

The issue is due to come to the foreground on Wednesday when the devolved Catalan parliament meets for the first time since Madrid suspended it after the region's independence referendum last October.

Spanish prime minister Mariano Rajoy warned on Monday that if they went ahead on Puigdemont then he would maintain direct rule over Catalonia under Article 155 of the Spanish constitution.

"To be sworn in, you have to do so physically. Realism and common sense should prevail," he said in a speech at the HQ of his Popular Party in Madrid.

"It [direct rule] will remain in force until the new president takes possession [of the role]," he added.

Spanish authorities have also set up controls on Catalan roads and airports to arrest Puigdemont if he tried to return, Spanish media reported.

But the European Commission backed Madrid's tough line on Tuesday.

"Separation of powers [in Spain] is clear and well defined, where all citizens, from Catalonia or other parts of Spain, are protected by the law and if they violate the law, they have to face consequences", Frans Timmermans, the commission vice president, told press in Strasbourg.

Puigdemont and four other separatist politicians fled to the Belgian and EU capital last year after Spanish prosecutors called for him to face a 20-year jail sentence for his role in the independence referendum, which was deemed illegal by the Spanish constitutional court.

The pro-independence side won by a whopping 92 percent, but the low turnout (43%) added to questions on the vote's legitimacy.

The events have seen Ciudadanos, a liberal Spanish party which originated in Catalonia and which opposes independence, climb in support.

Ciudadanos came top in the Catalan election in December.

Rajoy slipping

A poll by Metroscopia for the El Pais newspaper last week said it has also become the most popular party in Spain ahead of elections in 2020, with 27 percent support compared to Rajoy's centre-right Popular Party on 23 percent and the centre-left PSOE party on 22 percent.

"As a party we made mistakes, we recognise them and we will have to learn from them," Rajoy also said on Monday.

"The government's response to this situation has been good for Spain even if it wasn't good for the People's Party," he added, referring to his handling of the Catalan crisis.