The Socialist Party in Spain's southern Andalusia has declined on Thursday to present a candidate for investiture as regional president after center-right parties arrived at an agreement with the far-right newcomer Vox party to back one of their leaders for the post, the party said.

Susana Diaz, whose Socialist Party PSOE obtained the most votes but not an absolute majority in regional elections on Dec. 3, has acknowledged that she will have to lead the opposition following an agreement reached late Wednesday by the right-of-center Popular Party and business-friendly Ciudadanos with ultra-right Vox to back the PP's Juanma Moreno as the new president of Andalusia.

"An agreement has been signed between the right and the extreme right and, obviously, we thus have the leadership of the opposition which is going to be led by Susana Diaz," regional PSOE spokesman Mario Jimenez said.

The PSOE, which had governed uninterrupted in Andalusia for the past 36 years since the country's regional autonomy arrangement was established in 1982, suffered a stinging reversal on Dec. 3, garnering just 33 parliamentary seats to the PP's 26, Ciudadanos' 21, the leftist Adelante Andalucia's 17 and 12 for Vox.

This opened the way for a coalition of the PP and Ciudadanos to govern the populous southern region with Vox's backing during voting.

Diaz could still attend the plenary session in Andalusia's regional parliament if something were to go awry and Moreno's investiture was frustrated, Jimenez added.