Madrid has said it will sue Artur Mas, the Catalonian president for “disobedience and dishonesty” after Sunday’s independence vote, which saw 80 percent backing a split from Spain. Mas defied a court injunction barring him to hold a succession vote.

Court sources have said the details of the case against Mas are being finalized and will probably be filed on Thursday, Reuters reports.

Although the independence vote was informal and non-binding, it saw 2 million out of a possible 5.4 million people take part, in which 80 percent voted for independence.

READ MORE: 80% of Catalans say 'Yes' to independence in symbolic ‘referendum’

Mas hailed the vote as “a great success” but it immediately drew harsh criticism from the Spanish government.

Justice Minister Rafael Catala dismissed it as “a sterile and useless sham” and “a day of political propaganda.”

However, Prime Minister Mariano Rajoy says he wants to open up dialogue with Mas.

On Tuesday, Mas said he is keen to start discussions over Catalan independence and other measures to help the economy of the region, which accounts for about a fifth of Spain’s economic output and population.

And while Rajoy has said he will never agree to a legal vote on independence for Catalonia, he has said that he may budge slightly on reforming the constitution to give the Catalans some powers of their own on spending and taxation.