Luis Barcenas was sentenced earlier this month to 33 years and four months in prison and fined €44 million ($51 million) for his role in a vast system of bribes given to former PP officials or lawmakers in exchange for juicy contracts.
Barcenas, who was the PP's treasurer between 2008 and 2009, was accused of being in charge of a party slush fund and suspected of having hidden millions of euros in Switzerland.
The trial, which saw a total of 29 former officials, businessmen and their spouses jailed, is just one of many corruption scandals to have hit Rajoy's PP over the years, prompting the parliamentary no-confidence vote due at the end of the week.
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Spain's National Court, which deals with major criminal cases, said Monday it had sent Barcenas straight to prison instead of bailing him pending a possible appeal.
Guillermo Ortega, the former PP mayor of Majadahonda near Madrid who was sentenced to 38 years and three months in prison was also jailed immediately, as was a former PP regional minister.
The National Court will on Wednesday decide on the fate of others who were also sentenced to jail.
Judges also found that the PP itself had benefitted from illegally obtained funds although the party was not on trial for direct involvement in the scheme. The PP was ordered to pay back €245,000.
The court also confirmed the existence of a "slush fund" within the PP
which is the subject of another pending trial.
Together it prompted the opposition Socialists to file a no-confidence motion against Rajoy on Friday.
The parliamentary debate and vote will take place on Thursday and Friday.
Socialist party chief Pedro Sanchez said people's "trust in politics" was at play.
To succeed, the motion will need the support of an absolute majority of 176 lawmakers, a difficult task as the opposition parties are deeply divided.
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