The chief defendant in the trial of Catalan independence leaders declared himself a political prisoner as he took the stand on Thursday in the Madrid court where he and 11 others face charges over the 2017 bid to break away from Spain.

Oriol Junqueras, the former Catalan vice-president, effectively refused to recognise the court, agreeing only to take questions from his defence lawyer and not the prosecution. “This is a political trial and I refuse to answer to my accusers,” he said. “I am a political prisoner and I am on trial for my ideas.”

Junqueras is one of 12 politicians and grassroots activists on trial for their part in the illegal referendum and unilateral declaration of independence in Catalonia in 2017. Nine of the accused, among them the former speaker of the Catalan parliament, Carme Forcadell, are accused of rebellion, which carries a prison sentence of up to 25 years.

“Nothing we have done is a crime and we are innocent of the crimes we are accused of,” Junqueras, the leader of the Republic Left party, said during two hours of questioning by his lawyer, Andreu van den Eynde, on the third day of a trial that is expected to last up to three months.

“We are republicans first and then separatists, but above all we are democrats,” he said. “We are convinced that a republic of Catalonia is the best way to create a just society. We have always pursued this goal and will continue to do so, whatever the outcome of this trial. Sending us to jail won’t solve anything.”

He insisted that the 2015 Catalan regional election had been held as a plebiscite on independence, and given that separatists won a majority they were carrying out their democratic mandate by pursuing independence through a referendum and unilateral declaration.

Manuel Marchena, the chairman of the seven judges hearing the case, had earlier refused a request for Carles Puigdemont to appear as a witness.

“He can’t be a defendant in the morning and a witness in the afternoon,” Marchena said of the former Catalan president, who lives in self-imposed exile in Belgium and has said he expects a new European warrant for his arrest to be issued soon.

Marchena also ruled out simultaneous translation from Catalan into Spanish, claiming that at no point during the 16 months of preliminary hearings had this been requested. He conceded the right of defendants to respond in Catalan, however, with a consecutive rather than simultaneous translation.

Junqueras said at the start of his testimony that he was happy to speak in Spanish so that he would be as widely understood as possible. His decision to make a political defence may put him at odds with his fellow defendants, however, several of whom are expected to mount a legal challenge to the charges.

After Junqueras it was the turn of Joaquim Forn, the former interior minister, to take the stand. He agreed to be questioned by the prosecution. Forn, who was in charge of the Catalan police force, the Mossos d’Esquadra, said it had never acted in a way that infringed the constitution.

He insisted the force had obeyed the high court’s instructions to prevent the 1 October referendum from taking place, claiming that it was the biggest operation it had ever mounted.

The day’s proceedings were overshadowed by remarks made by Irene Lozano, the secretary of state for Global Spain, who compared the independence referendum to rape.

“They wanted a referendum but they didn’t have permission,” she told Sky News. “Using sex as a metaphor, if you don’t have permission, it’s rape.”

Lozano later tweeted that the referendum had been divisive but admitted her choice of words had been unfortunate. Global Spain was established to improve the country’s image at home and abroad.