The Catalan leader, Artur Mas, formally called a November referendum on independence on Saturday, in a show of defiance that puts the wealthy north-east region of Spain on a collision course with the central government in Madrid.

Mas's signature on a decree allowing the vote to go forward came one week after the Catalan parliament passed a law paving the way for non-binding consultations in the region. As the solemn signing ceremony took place yesterday yesterday morning, government officials crowded around the document, excitedly snapping photographs on their mobile phones.

"Catalonia has the right to decide its political future," said Mas. "We know that democracy is the most civilised way to resolve difficulties between nations." The 9 November referendum would see two questions put to Catalans: whether Catalonia should be a state and, if so, whether it should be an independent state.

The central government has repeatedly insisted that any regional vote on independence would be illegal, pointing out that the country's 1978 constitution means major questions must be put to all Spaniards and that only they can call a referendum. Barcelona, in turn, asserts that the non-binding nature of its regional vote allows it to take place within the legal confines of the constitution.

Recent days have seen the People's Party government in Madrid make it clear that no such vote will take place on its watch. On Saturday the deputy prime minister, Soraya Sáenz de Santamaría, vowed that the central government would immediately seek to have the Catalan law and decree struck down by the country's constitutional court. "This referendum is unconstitutional and will not take place," she said, adding: "We deeply regret the initiative of the president of Catalonia and believe it is an error. It fractures Catalan society, divides Catalans and pushes them further away from Europe." Prime minister Mariano Rajoy, who on Saturday was flying back from China, has convened a cabinet meeting on Monday.

Undeterred by the outcome in the Scottish referendum, Mas has instead seized on the Scottish precedent to insist that Catalans be allowed the same opportunity to vote. "We're open to compromise, but we can't fall into inaction," said Mas on Saturday.

Catalonia is home to about 16% of the Spanish population and accounts for nearly one-fifth of Spain's GDP. Central government is wary that any concessions to Catalans might have to be extended to other regions such as the Basque country.

Despite predictions that the referendum could be suspended by the constitutional court as early as this week, hundreds of pro-independence and pro-referendum campaigners gathered outside the regional government headquarters in Barcelona, waving Catalan flags as Mas signed the decree inside. Campaigners also put up a ticker on a nearby building, counting down the days until the vote.

The grassroots movement to break away from Spain has strengthened alongside the obstinacy of the central government; while in 2010 one-fifth of Catalans supported independence, by 2013 the number hovered around half, according to Catalonia's Centre for Opinion Studies.

Once the vote is brought to the constitutional court, few expect the tribunal to rule in favour of Catalonia. Trapped between an electorate clamouring for a vote and an inflexible Madrid, the suspension would leave Mas with few cards to play. He could call early elections in the region or push forward with an illegal vote, risking arrest and the suspension of Catalonia's autonomy.

Still, Mas is under pressure to defy any court order by the pro-independence Catalan Republican Left (ERC), the left-leaning party that props up his minority government. It is this party that analysts predict could make big gains if Mas were to call early elections, leaving Madrid staring down a Catalan government more ardently committed to independence. Earlier this month, ERC leader Oriol Junqueras said that Catalans should consider civil disobedience, "just like Martin Luther King," if the central government denies them the chance to vote.

As Madrid and Barcelona butt heads in an escalating political conflict, Spain's Socialist party has become increasingly vocal about their long-championed alternative solution. The party, which backs Rajoy's government in its court challenge of the vote, is suggesting a constitutional overhaul for Spain, one that would define clear powers and responsibilities for Spain's regions and seek to recognise the country's diversity. As leader Pedro Sánchez wrote last week in El País, so far little has been achieved by the political stalemate between Madrid and Barcelona. He added: "After 9 November goes by and there is no vote, we'll have to face the emotions in Catalonia; frustration, anger, discouragement and even resistance."