Leaked to the media, forged information created by the police alleged Podemos was originally financed with money from Iran and Venezuela
The news that, under previous conservative governments, Spain's "political police" allegedly dug up dirt and fabricated evidence to harm political opponents, has emerged as an explosive controversy in the campaign for elections at the end of this month.
The existence of these secret operations came to light in 2016 when a leaked conversation appeared to show then-Interior Minister Jorge Fernandez Diaz discussing ways to incriminate Catalan pro-independence politicians.
But as general elections near on April 28, new revelations have emerged in the media that the "political police" targeted far-left party Podemos when the conservative Popular Party (PP) was in power.
Fernandez Diaz, who was the Interior Minister from 2011 to 2016, denies any such operations took place.
But Socialist Prime Minister Pedro Sanchez confirmed on Spanish television channel La Sexta this week that there were "corrupt police" used to "obstruct judicial cases" and also "spy on various political rivals" under the previous government.
Ramon Cosio, a spokesman for the SUP police union, says this is all linked to an age-old Spanish practice of remodeling the police leadership after every change of government.
That has led to certain leaders being appointed "more for their proximity (to the ruling party) or ideological profile" than according to professional criteria, he adds.
Podemos, one of the political parties set to officially launch their campaigns on Thursday night, was of particular interest to this "political police," it has emerged.
Several former senior police officers are suspected of having fabricated fake evidence to discredit Podemos when it was expanding in 2015 and 2016.
Leaked to the media, the information alleged Podemos was originally financed with money from Iran and Venezuela, where party general secretary Pablo Iglesias and several other colleagues had once advised the government of late leader Hugo Chavez.
The allegations were brought to court, which never found any evidence to support them and shelved them.
In further proof, Rafael Isea, who was Venezuela's finance minister in 2008 before falling from grace, told Spanish television earlier this month he endorsed information about Podemos in exchange for an offer to give relatives Spanish residency.
He said he met one of the Spanish police's top officers, Jose Angel Fuentes Gago, in 2016 in New York.
He alleged Fuentes Gago made him endorse a fake document that was later leaked which detailed an alleged payment of seven million euros (US$7.9 million) from Chavez's government to a political consultancy where Iglesias and others worked before founding Podemos.
The far-left party's leader Pablo Iglesias hit back, telling Spanish radio that the operation against his party equated to "subverting Spanish democracy."
Pablo Casado, who now heads up the PP after his predecessor Mariano Rajoy was ousted from power in a no-confidence vote last June, even admitted there was "less than exemplary" behavior in the Interior ministry at the time.
Adding fuel to fire, details of how false information ended up in the media also emerged this week.
After being questioned by a judge, Alberto Pozas, who until Friday was one of the government's communications directors, was put under investigation for alleged breach of confidence.
A judicial source, who refused to be named, said Pozas told the judge he received embarrassing information, retrieved from a stolen smartphone, about Iglesias in 2016 when he headed up the magazine Interviu.
He did not publish the information but gave it to Jose Manuel Villarejo, a former police chief who for years covertly recorded conversations with the all-powerful and attempted to blackmail them.
The information on Iglesias was later published in other media, presumably leaked by Villarejo.
The 67-year-old is now behind bars, suspected of large-scale corruption, but continues to reveal compromising information that has embarrassed government figures and even the monarchy.
In his book "The Director," published April 8, former editor of the El Mundo daily David Jimenez writes Villarejo had been the "facilitator of most of our exclusives" for years.
He says he was offered "two reports on Podemos" which he discarded, judging they lacked "seriousness."