Today's revelations in El País newspaper of a double-accounting system that allegedly ran until recently in Spain's ruling People's party (PP) raises the awful spectre that those who are now busy hiking taxes and cutting spending are tax cheats.

While the documents published by El País refer to the period between 1997 and 2008, and the party has reportedly since cleaned up its act, they suggest that a cash-in-hand payment system saw money moving beyond the reach of tax authorities.

And while it has not been proved that the individuals named in the alleged accounts, including the prime minister, Mariano Rajoy, the party general secretary, María Dolores de Cospedal, and the former IMF boss Rodrigo Rato, really did receive the money (or fail to pay taxes on it if they did), the PP is already so deep in corruption scandals that ordinary Spaniards may have trouble believing the party's denials.

Rato and Cospedal have both insisted they did not receive the money noted down in the accounts, while Cospedal issued a denial in Rajoy's name.

Crusading former magistrate Baltasar Garzón, who was disbarred last year precisely because he wrongly ordered the secret recording in prison of conversations between lawyers and remand prisoners accused of PP-related corruption, may be celebrating today.

The PP's protestations of innocence are spoiled by the fact that one of the men alleged to have run the double-accounting, its former treasurer Luis Bárcenas, was recently found to have a €20m secret bank account in Switzerland. Bárcenas has admitted that, during a tax amnesty approved by the PP government last year, he declared €11m that had previously been hidden. He is already under investigation by the courts.

Bárcenas is known to have taken away boxes full of documents from the PP headquarters – provoking concern that he might blackmail the party - but sources tell me he did not provide the accounts books to El Pais.

The party claims it is the victim of dirty tricks and conspiracies, but it also used that excuse when it, at first, tried to support Bárcenas. It has since cut the former treasurer adrift.

Cospedal also claims this has no impact on Rajoy's ability to run the country. Time will be the judge of that.