Seven years after taking office by ousting corruption-ridden conservatives from government, Pedro Sánchez is fighting for his political life amid investigations into alleged graft in his Socialist party (PSOE).

On June 12, an ashen-faced prime minister apologised to Spaniards after audio gathered by civil guard investigators was made public and appeared to show the PSOE secretary, Santos Cerdán, discussing commissions paid by companies in exchange for public contracts.

Sánchez has not himself been directly implicated, but the Socialist leader who came to power promising to clean up politics is now facing calls to resign from an invigorated opposition.

Cerdán, who was party number three, has resigned from the PSOE and stepped down as a member of parliament. He is due to appear before the Supreme Court on 25 June. He maintains he has never committed a crime nor been implicit in one.

The investigation into commissions is part of an ongoing probe which has already implicated José Luis Ábalos, a former PSOE secretary and transport minister. A third person implicated is Koldo García, an advisor to Ábalos. Both men featured with Cerdán in the recently exposed audio. All three say they have done nothing wrong.