The president of the Spanish region of Catalonia has written to European Union leaders asking them to support his plans to hold a referendum on independence later this year.

The Spanish government insists that such a referendum would be unconstitutional, saying last month that it “guaranteed” a referendum will not take place. But Artur Mas says in his letter, which was sent in December but made public yesterday (2 January) on his official website, that there are “a number of legal and constitutional options which allow this referendum to take place”.

Mas said that the poll result would be consultative rather than legally binding. But a ‘Yes’ vote would put pressure on the Spanish government to begin talks on secession. Mas wants the referendum to be held in November, just two months after Scotland holds a referendum on independence.

Support from other EU leaders may be crucial to the cause of both Scottish and Catalonian independence. The European Commission has said that any new member states resulting from secession would need to apply for EU membership.

Admission to the EU would require unanimous consent from all member states, and may be resisted by countries with their own separatist movements. Spain could theoretically block Scotland from entering the EU, and the UK could block Catalonia from doing the same. Both the Catalan and Scottish governments have insisted that they should not have to apply for new membership.

So far, no EU leader outside Spain has made any comment on the Catalan referendum. Mas did not send the letter to the leaders of the EU institutions, but to national leaders.