Spain’s conservative People’s party (PP) won Sunday’s Andalucían regional election, but lost its absolute majority, leaving it dependent on the support or abstention of the far-right Vox party to form a new government.

After the poll in Spain’s most populous region – which will serve as a barometer of wider electoral opinion ahead of next year’s general election – the socialists slumped to an all-time low and Vox picked up one additional seat.

The PP took 53 seats in the 109-seat regional parliament, leaving them two seats short of an absolute majority and five down on the 58 they won at the last election in 2022.

The Spanish Socialist Workers’ party (PSOE), which is led nationally by the prime minister, Pedro Sánchez, dropped from 30 seats to 28, while Vox climbed from 14 seats to 15. The leftwing Adelante Andalucía party climbed from two seats to six, and the leftist coalition Por Andalucía held on to the five seats in won four years ago.

Sunday’s results mean that the regional PP leader, Juan Manuel “Juanma” Moreno, will have to negotiate his return to office with Vox – something he was keen to avoid during the campaign.

“I’m going to try to govern alone and I’ll work as hard as possible to so there are no constraints or conditions from Vox,” he told Cadena Ser radio last week. “I’ve said very clearly that I have no interest in governing with Vox. None at all.”

Moreno has criticised the far-right party’s so-called “national priority” policy, which would favour Spaniards over foreign-born people when it comes to housing and benefits. Although Moreno dismissed it as “an empty slogan”, Vox has made the policy a key part of the coalition agreements it has recently reentered with the PP in regions such as Extremadura and Aragón.

Speaking after the results came in, Moreno said his party had come very close to another absolute majority, but that the arithmetic had always been complicated.

“It’s true that we didn’t get top marks we were hoping for, but we’ve still achieved and outstanding grade” he said. Moreno also insisted he had been given an mandate “to continue transforming Andalucía”, and promised “four more years of reforms and stability”.

The PP, which could now face months of negotiations with Vox to form a new government, described its win as a “resounding victory” and said Sánchez’s socialists had suffered “a catastrophic result”. The prime minister congratulated Moreno but said his party would “continue to drive the kind of social and political advances that improve people’s lives”.

Vox’s leader, Santiago Abascal, called on Moreno to heed the voices of the 576,000 Andalucíans who had backed his party and thereby shown that they “believe in national priority … and believe that regional governments can work to stop the migrant invasion”.

Polls leading up to next year’s general election suggest the PP is on course to defeat Sánchez, whose inner circle, party and administration have been battered by a series of corruption scandals. However, the conservatives are expected to fall short of an absolute majority and would probably need Vox’s support to govern at a national level.