A far-right party has won seats in a Spanish regional parliament for the first time since the country returned to democracy following the death of longtime dictator Francisco Franco in 1975.

With 99% of the votes counted in Andalucía, the small Vox party took 12 seats in the 109-member regional parliament.

The Socialists won the election, but saw their support plummet to just 33 seats, compared to 47 in 2015 – far from the majority of 55 seats needed to govern.

The result means that Vox, which opposes illegal immigration and Catalan independence, has exceeded even the most optimistic poll predictions which had forecast a possible five seat win. The party’s platform includes restricting abortion and rolling back domestic violence laws.

Vox had not previously held any seats in any legislative body in Spain since its founding four years ago, and now it has the key to forming a government in the nation’s most populated region.

“Now is the moment to say loud and clear who we are and that we have come to stay,” Vox candidate Francisco Serrano told a crowd of supporters who chanted: “Spain! Spain! Spain!”

Andalucía has been a Socialist bastion for 36 years, but the party could lose control of the government if parties on the right join forces to oust regional leader Susana Diaz, though that would require that they join forces with Vox.

“Despite winning the election it is a sad night for the Socialist Party,” Diaz said.

“There has been a real loss of ground for the Left. But the worst thing is that the extreme right, a phenomenon that has appeared in the rest of Europe, has arrived here.”

Diaz said she would call on other parties to “build a firewall against the extreme right in Spain.”

“Each party must decide if they are against the extreme right or if they will rely on their support to enter into government,” she said.

The Socialist Workers’ Party (PSOE) scored the worst result in its history winning 33 seats so far.

Its potential ally on the left Adelante Andalusia (Forward Andalusia) picked up only 17 seats, depriving the left of a majority, while the conservative Popular Party (PP) won 26 seats and the Ciudadanos liberals took 21 seats.

The poll had been seen as the first of a series of tests for Socialist prime minister Pedro Sanchez.

It was Sanchez’s first electoral test since taking office in June after winning a surprise vote of no-confidence in parliament against the previous PP government of Mariano Rajoy over a corruption scandal.

His Socialists had ruled Andalusia since 1982.

The vote is a mere foretaste of the coming “super election year”: 2019 will see municipal, regional and European elections and perhaps even an early general election to coincide with the other May polls.

All eyes will now be on Vox, which could try to use Andalusia as a springboard in next year’s elections.