The separatist movement in Catalonia’s parliament has escalated its battle with Madrid after it defied Spain’s constitutional court by debating a controversial pro-independence roadmap, and the region’s president announced a confidence vote to consolidate the move towards sovereignty.

The angry, last-minute debate – in which the pro-independence Together for Yes coalition and the smaller, far-left Popular Unity Candidacy secured approval for the unilateral disconnection plan by 72 votes to 11 – represents another open challenge to the Spanish judiciary and to Spain’s acting prime minister, Mariano Rajoy.



It also provoked a furious reaction in the Catalan parliament from Ciudadanos and Popular party MPs who left the chamber rather than take part in a vote they described as “illegal” and flagrantly undemocratic. One Ciudadanos MP accused the separatist faction of “wanting to take us not only out of Spain and the EU, but out of the 21st century and modern democracy”.



However, the president of the Catalan parliament, Together for Yes’s Carme Forcadell, insisted the parliament was exercising its sovereign rights.



Earlier on Wednesday, the pro-separatist Catalan president, Carles Puigdemont, said a confidence vote would be held in parliament on 28 September to help bring the region to “the gates of independence”.



Last November, the Catalan parliament voted to begin the process of breaking away from Spain after separatist MPs used their majority to pass legislation to effect a “disconnection from the Spanish state” and pave the way for an independent Catalan state.



Spain’s constitutional court responded by unanimously ruling that the legislation had ignored and infringed the rules of the 1978 constitution, adding that the “principle of democracy cannot be considered to be separate from the unconditional primacy of the constitution”.



Rajoy hailed the court’s decision as a victory for “the majority of Spaniards who believe in Spain, in national sovereignty and in the equality of all”.



Spain’s acting deputy prime minister said the behaviour of the Catalan parliament would not be tolerated, adding that a cabinet meeting on Friday would authorise the government’s legal team to file a challenge with the constitutional court.

“The government said that we would not let allow any steps to be taken,” said Soraya Sáenz de Santamaría. “Yet today another very serious and obstinate one has been taken, one that infringes the right of all Spaniards to decide their constitutional framework. The government has said it will act, has been acting and will act.”

Pedro Sánchez, the leader of Spain’s socialist party, said the Catalan parliament’s decision was “extraordinarily serious” and had disregarded the rulings of the constitutional court.

He added: “No one has the right to put institutions beyond the law. These decisions violate the constitution and Catalonia’s statutes.”

The issue of Catalan independence remains bitterly divisive in both Spain and within the region itself. A recent poll suggested that 47.7% of Catalans are in favour of separating from Spain, while 42.4% were against it, with 8.3% undecided.



In an interview with the Guardian in the run-up to the vote, Forcadell and Raül Romeva, the Catalan foreign affairs minister, said Madrid’s failure to engage with the independence debate had left the government with no choice but to forge its own separatist path.



“The [Spanish state] has left us feeling that we just don’t have an alternative,” Romeva said. “We have always said that we would have preferred a Scottish-type scenario, where we could negotiate with the state and hold a coordinated and democratic referendum. We keep talking to Madrid, but all we get back from them is an echo.”



Romeva said the Spanish government had two options: accept the reality of Catalan independence or “carry on doing what it’s been doing, which is denying that reality in the belief that it can use the constitutional court and legal processes to stop it”, he said.



The latter path, Romeva said, would continue to prove to be counter-productive. “Every action they take serves only to rearm us and give us greater legitimacy for what we’re doing,” he said.

Since winning the Catalan election last September, the government, led by the Together for Yes coalition, has begun preparing legal steps for the transition and designing a tax collection authority, a social security apparatus and a foreign affairs department.

The aim, according to Romeva, is to have the necessary structures in place for when another independence referendum is called, likely in a year’s time.



Although the Spanish state is implacably opposed to Catalonia’s secession, with Rajoy having vowed to use “all political and judicial mechanisms in defence of the common good and the sovereignty of Spain as laid down in the constitution,” Romeva insists that Madrid has a democratic responsibility to accept the will of the majority of Catalans.



“The Spanish government uses the question of legality a lot,” he said. “But legality is an instrument; it needs to adapt to reality and to democratic will, and not the other way round. People around the world need to understand that what we’re doing is fundamentally legitimate and is not illegal.

“I’m being very careful with my words: it’s legitimate and it’s not illegal. It’s true that the [Spanish] constitution says what it says. But constitutions are texts that exist to serve a particular moment in history and certain circumstances.”

Romeva then hinted that even if the Spanish courts ruled against independence, it would not prevent the push for secession.

“Even if it were [illegal] – and it’s not – if there were a legitimate, peaceful and majority demand, it’s the law that would need to change. It’s a democratic right. You might not agree with it, but you can’t deny the democratic principle,” he said.



Raül Romeva. Photograph: Jorge Guerrero/AFP/Getty Images

The Brexit vote in the UK, which has been closely followed in Catalonia, had revealed the “democratic deficit” in Europe and the need for the EU to recognise the dissatisfaction within its ranks, Romeva said. He denied that it would have a positive effect on Catalonia’s independence project by forcing the EU to entertain the prospect of a significant realignment, but said it had underlined the need for negotiation.

“Brexit isn’t good news for Europe or for Catalonia,” Romeva said. “It’s worrying, because it calls the European project into question. It feeds the frustration that Europe is in crisis. From that point of view, it isn’t good news. But that said, when there is a situation of conflict, democracy is the tool you use.

“In Catalan logic, yes, we don’t like Brexit, but we understand that the democratic deficit in Europe is what allowed leave to win. A process of negotiation has begun: it’s not the end of the world and it’s not paradise.”



He also shrugged off the idea that an independent Catalonia might find itself outside the EU.

“We have hundreds of European companies in Catalonia. The question is: if Catalonia became an independent state, in whose interests would it be for Catalonia to be out of the EU? Not Catalonia’s. Not Spain’s either,” Romeva said.

“Catalonia is and will be an ally of Spain for obvious reasons of markets and infrastructure, as well as cultural and linguistic reasons. Europe wouldn’t want to lose such an economically and socially dynamic reality. So this unthinking assumption that an independent Catalonia would be kept out [of the EU] is false.”