Spain’s prime minister, Pedro Sánchez, has compared Brexit to the failed push for Catalan independence, warning that “engaging in campaigns or political projects based on lies eventually leads societies down a blind alley”.

Renewing his appeal for the UK to accept the EU’s withdrawal deal, Sánchez said he saw clear parallels between the rhetoric that drove the Brexit debate and the arguments used in the regional independence campaign that plunged Spain into its worst crisis in four decades.

“The techniques of the Catalan independence movement are very similar to those of [Nigel] Farage and other ultra-conservative leaders who have defended Brexit,” he said.

“They say, ‘Europe’s stealing from us!’, or ‘Spain is stealing from us!’, or, ‘If we had more economic resources …’. At the end of the day, I think that engaging in campaigns or political projects based on lies eventually leads societies down a blind alley and that’s really hard to manage.”

Sánchez said lessons needed to be learned from Brexit – not least how internal differences in a single political party can swell into “a global problem”.

In a joint interview with the Guardian, Le Monde, Frankfurter Allgemeine Zeitung and La Repubblica, the socialist premier said democracy “isn’t just heads or tails” and that Brexit should never have been presented as a binary issue.

“It’s not ‘Do I leave or do I stay?’ Maybe the question that should have been asked was, ‘Do you want to stay in a better Europe?’, because there are certainly lots of things that need to change in Europe.”

People celebrate in Barcelona after Catalonia’s parliament voted to declare independence from Spain. Photograph: Pau Barrena/AFP/Getty Images

Although Sánchez said he had been struck by the generation gap evident in the anti-Brexit demonstrations – “young people are in favour of remaining and they’re the future of the UK” – he said he hoped MPs would ensure the UK’s exit was as managed and painless as possible.

“I think the message to send is that this is the only possible and viable deal,” he said.

“The UK parliament is facing a dilemma that will require all its MPs to act responsibly to avoid a hard, disorderly Brexit. The possibility of an orderly Brexit still exists and that’s the appeal I’m making to British MPs.”

Sánchez added that while Spain and the UK have had disagreements – particularly over Gibraltar – he and Theresa May had maintained “a very close relationship” and were intent on protecting the rights of Spaniards in the UK and Britons in Spain.

He also noted the irony that, in May, “a politician who was in favour of remaining is the one now tasked with leading Britain’s departure from the European Union”.

Sánchez’s Spanish Socialist Workers’ party (PSOE), which took power last June after using a no-confidence motion to topple the corruption-mired conservative administration of Mariano Rajoy, is hoping to be returned to office in the general election on 28 April.

The government announced the poll – Spain’s third in less than four years – after failing to secure parliamentary support for its 2019 budget.

The budget plan was rejected in February by the rightwing People’s party, the centre-right Citizens party, and by the Catalan separatist parties who had backed Sánchez’s successful move to turf Rajoy and the PP out of office.

Polls suggest PSOE will increase its share of the vote in the election and become the largest single party in the 350-seat congress of deputies. Its current seat count – 84 – has made life difficult for the Sánchez administration.

Two of his ministers have resigned in the past 10 months, three others have faced scrutiny from the media and political opponents, and a series of U-turns have also damaged his fledgling administration.

However, things are also complicated for the Spanish right.

The PP’s years of hegemony are under sustained attack from both Citizens and the upstart Vox party, which won 12 seats in Andalucía’s regional parliament, becoming the first avowedly far-right party to triumph at the ballot box since Spain’s return to democracy after the death of Francisco Franco in 1975.

The party then cemented its influence by throwing its weight behind the PP-Citizens coalition that now governs Andalucía.

Vox’s breakthrough, fuelled partly by anxieties over the Catalan independence crisis, has pushed the PP and Citizens further to the right in an attempt to hang on to voters.

Both parties have attacked Sánchez’s more conciliatory approach to the Catalan question. A recent attack on the prime minister by the PP’s new leader, Pablo Casado, featured a litany of insults including traitor, squatter, villain, catastrophe, hostage and compulsive liar.

Meanwhile, the Citizens’ leader, Albert Rivera, has categorically ruled out any post-election pact with Sánchez.

Sánchez worries about the creeping influence of the far-right Vox party after its success in Andalucía. Photograph: Marcelo del Pozo/Reuters

While Sánchez is confident the likes of Vox will never win an election, he worries about its creeping influence on others, and its king-making power in Andalucía.

“What troubles me is the way they’re radicalising and swelling the political discourse of the PP and Citizens,” he said.

“Citizens calls itself a liberal party but, unlike other liberal parties in Europe – whose leaders say they don’t want to make deals with the far right – it has made a deal with the far right … Instead of putting a cordon sanitaire around the far right, it’s thrown one around social democracy.”

Sánchez is adamant the PSOE intends to govern alone, but is careful not to rule out any possible deals with anyone – including the Catalan pro-independence parties that helped torpedo his budget. “I will talk to all political parties but always within the bounds of the constitution and what is legal,” he said.

He is also sanguine about the length of time it is taking to finalise his government’s most symbolic act, the removal of Franco’s body from its vast mausoleum outside Madrid.

After numerous delays, the dictator is finally due to be exhumed and reburied in humbler surroundings in June.

“We’ve waited 40 years – a few more months won’t matter,” said Sánchez.