That option was backed by 70pc of the party's supporters that participated in an internal vote, Podemos said.

Sanchez - who won the most votes in a parliamentary election in April but not a majority - has so far rejected Podemos' demand of a full-fledged coalition government in exchange for their support in the confirmation vote in parliament next week.

The acting premier insisted on Thursday that he does not want Podemos leader Pablo Iglesias in his government but said he was open to other Podemos members with specific expertise.

Sanchez needs an absolute majority in the first parliamentary vote on Tuesday or, failing that, a simple majority in a second vote next Thursday, which he will struggle to obtain if Podemos rejects his bid.