The Catalan government has intensified its war of words with Spain by vowing to use its democratic mandate to forge a separate Catalan state with or without the approval of Madrid.

Catalonia is preparing to defy Spain’s constitutional court this week by debating the conclusions of a working group on sovereignty, nine months after the Catalan parliament put forward a resolution calling for the “beginning of a process of the creation of an independent Catalan state”.

Carme Forcadell, the president of the parliament, and Raül Romeva, the minister of foreign affairs, told the Guardian enduring hostility from Madrid had left Catalonia with no choice but to press ahead with the independence agenda.

“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.”

Forcadell pointed to a recent scandal as evidence of the Spanish government’s attitude towards Catalonia. Last month, Spain’s interior minister, Jorge Fernández Díaz, and the head of Catalonia’s anti-fraud office, Daniel de Alfonso, were apparently recorded discussing possible investigations that could be launched against pro-independence politicians in the region.

Forcadell said she was incredulous at the idea that the acting Spanish government, led by Mariano Rajoy, could simply brush aside the alleged incident and say nothing was going on.

“How can they say that when the interior minister, who’s meant to defend the interests of all citizens, is caught conspiring to find evidence against citizens solely because they think differently? How can absolutely nothing come of that? We don’t understand it,” she said.

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 counterproductive. “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 Junts pel Sí (Together for Yes) coalition, to which Forcadell and Romeva belong, 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. Together for Yes has been buoyed by a recent poll showing that 47.7% of people in Catalonia are in favour of independence.

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.

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.”