PP head Alberto Nunez Feijoo. | Juan Carlos Caval

Spain's main opposition People's Party (PP) is poised to win a parliamentary election in December but could only achieve a working majority via a potentially problematic alliance with the far-right Vox, according to an opinion poll published on Monday.

The survey carried out by private pollster GAD3 put the Socialist-led leftist ruling coalition of Prime Minister Pedro Sanchez behind PP, and short of a majority even combined with all its traditional and occasional allies in parliament. The conservative PP would win 32.4% of the vote, or between 139 and 143 seats in the 350-seat lower house, largely in line with where it stood in the previous GAD3 poll in November.

The Socialist Workers' Party (PSOE) was nearly 5 points behind and with a maximum of 111 seats, contrasting with a poll released on March 17 by the state-owned Centre for Sociological Studies (CIS) that put the Socialists ahead. Still, their standing improved slightly from the previous GAD3 survey and their junior coalition partner, the far-left Unidas Podemos, was steady at 8.9% of voting intentions, despite a recent rift over gender politics and other issues within the alliance.

Meanwhile, the anti-immigration Vox, that opposes feminism, and policies that favour LGBT and other minority communities, edged higher to 14.9%, or 43-45 seats, still below their election result in 2019 when they won 52 seats. Independents and regional parties would garner 30 seats in the elections and most of them would be more likely to back a leftist coalition than a PP-Vox alliance, which the parties have only tested in a handful of regions with mixed results. PP head Alberto Nunez Feijoo has said he would rather not ally with Vox in parliament, but may have no other option. In May, Spain will hold municipal and regional elections that will help gauge support for the main political parties in the general election to be held in December.