Spain’s ruling Partido Popular party has issued its most severe warnings to date to Catalan premier Carles Puigdemont over the consequences of tomorrow’s widely predicted declaration of independence, with a PP spokesman saying he could end up like the historic Catalan leader Lluís Companys – in jail.

“Anybody that declares it could end up like the one who tried it 83 years ago,” the PP’s deputy secretary for communication, Pablo Casado, said on Monday, in a reference to Lluis Companys’ failed bid for independence and subsequent spell in prison in 1934.

Mr Puigdemont is widely expected to declare independence in the regional parliament on Tuesday evening, nine days after the Catalan region voted for independence in a referendum dismissed by Madrid as illegal. Speaking with 24 hours to go, Mr Casado said the Prime Minister, Mariano Rajoy, planned to avail himself of every means provided by Spanish law and the constitution to fight any declaration.

Although he did not say which specific charges Mr Puigdemont might face, according to El Español, Mr Casado warned that in Spain the crimes of sedition carry a maximum prison sentence of 15 years and rebellion against the state 25 years. Mr Companys was himself sentenced to 30 years in jail.

“They [independence leaders] are going to run headlong into the [courtroom] dock,” Mr Casado predicted. “It’s going to cost them.”

Mr Casado was later careful to point out that his comparisons with Mr Companys had referred to the Catalan’s 1934 trial and incarceration after the independence bid, not to his subsequent capture, torture and execution by General Franco’s police in 1940.

“I meant that history should not repeat itself,” he explained, “and if you forget history, you’re condemned to repeat it. In history, declarations of independence by Catalonia have fared very badly.”

Mr Casado also insisted there was no room now for international mediation and that the Spanish government had “nothing to negotiate with the golpistas” – the Spanish word for conspirators in a coup d’etat.

Meanwhile, Deputy Prime Minister Soraya Saenz de Santamaria made what she called “an appeal to sensible people inside the Catalan government not to fling itself into the abyss.”

She bluntly described Mr Puigdemont as a “fanatic” and insisted that this is “why we need a double dose of common sense.”

“It [a declaration of independence] will not go unanswered,” she said, adding that “all measures necessary will be taken” in response.

The PP’s hardline attitude towards Mr Puigdemont has been given fresh momentum by Sunday’s massive pro-Spanish unity rally in Barcelona. But it also found further backing on Monday when the opposition leader Pedro Sánchez, head of the Socialist party, finally confirmed that his party would “stand by the [Spanish] state” if a declaration of independence materialised.