Spain’s political class needs to listen to the concerns of voters who support the far-right Vox party rather than dismissing them as extremists, the former French prime minister and Barcelona mayoral candidate, Manuel Valls, has warned.

Valls, who served as France’s prime minister under President François Hollande from 2014 to 2016, said Vox’s breakthrough in last week’s Andalucían regional election represented a serious challenge to the political status quo.

The tiny, far-right grouping won 11% of the vote and took 12 seats in the Andalucían parliament, becoming the first far-right party to win representation since the death of Franco in 1975.

“It’s an important political phenomenon and I think it’s one that is going to continue,” Valls told the Guardian.

He said Vox resembled other European nationalist populist parties, such as Marine Le Pen’s National Rally in France (formerly known as the Front National), La Lega (the League) in Italy and Alternative für Deutschland in Germany.

“A lot of people say, ‘Look, it’s only 11%’, but Le Pen and the AfD and La Lega always start that way, getting seats in parliament or in a municipal council,” said Valls. “And now they’re expanding because they’re at the centre of the political debate.”

He said that the end of Spain’s traditional, two-party political system had opened up space for Vox and others, while many in Andalucía had felt ignored by the big political parties.

Valls acknowledged that efforts to tackle the far right in Europe had so far proved unsuccessful amid what he termed the “political, social, economic and cultural crisis” engulfing the continent.

“The first thing we need to do is not insult voters,” he said. “I think there was another phenomenon in Andalucía, which is that people didn’t talk about the voters’ problems. There was very little of that, which is why there was a reaction against it.”

He said the main Spanish parties – the governing socialist PSOE, the conservative People’s party and the centre-right Citizens party – needed to “occupy the moderate centre” while also reclaiming patriotism from the far right.

“What has worked in France for many years – and what still works – is that the right has put up a cordon sanitaire and has always said that there will be no alliances with the Front National,” said Valls. “That’s happened from Chirac to Sarkozy and all the way up to Macron.”

Although the PSOE won the most votes in Andalucía, it is well short of a majority. The next regional government must be formed by the end of December and could see a PP-Citizens coalition – if the PSOE abstains – or even a possible agreement between the two rightwing parties and Vox.

Valls, however, said any such deal would be morally and politically compromising. “I think it would be a mistake for the PP, and for everyone, to make deals with Vox,” he said. [PP leader Pablo] Casado said Vox has the same values as the PP and I think that was a basic mistake.

“It’s not just a moral issue, it’s also a strategic mistake because you’re sending a signal to your voters. If you tell them another party shares the same values, they’ll be off. You’re giving them permission to vote for someone else.”

The best approach, he said, was to address people’s underlying concerns, such as immigration, the economy and the Catalan independence crisis.

Valls was born in Barcelona and is running as an independent mayoral candidate. But his campaign has been welcomed by the Citizens party. Its leader, Albert Rivera, has said: “There is no one better to recover Barcelona’s prestige and defeat separatism and populism at the ballot box.”

Valls, a staunch opponent of Catalan secession, said he was very worried by recent events in the region.Last week, Catalan riot police clashed with pro-independence activists protesting against Vox in the cities of Terrassa and Girona.

Catalonia’s separatist president, Quim Torra, has ordered changes be made to the regional force, the Mossos d’Esquadra, in the wake of the clashes.

Four of the Catalan leaders facing trial over last year’s failed push for regional independence have gone on a hunger strike, while dozens of separatist activists have been blocking a motorway in Tarragona.