Madrid ( CNN ) -- Just one day after a tense debate in Spanish parliament on how to stop political corruption , a leading newspaper published Thursday what it said were handwritten documents detailing 19 years of secretive payments to leaders of the ruling conservative Popular Party . El Pais newspaper said the alleged payments through 2009 -- off the party 's normal books -- went to Mariano Rajoy , a longtime party leader and Spain 's prime minister since December 2011 , and to numerous other current or former top party officials . Spain in 2013 : Is the worst over ? The party quickly issued a statement Thursday morning , denying any `` hidden accounts '' and insisting that all payments to party leaders have been `` legal and in compliance with tax obligations . '' Thursday evening , hundreds of protesters reacting to the report gathered near the ruling party 's headquarters . They were kept back a distance from the building itself by riot police on two ends of a long street . The protesters called for the prime minister to resign and sarcastically chanted , `` Our taxes are your envelopes , '' a reference to the secretive cash payments reported to have occurred . The latest allegations -- making headlines across all Spanish media -- came as corruption scandals , affecting several political parties and even the royal household , have rocked the nation during its deep economic crisis , with a recession and an unemployment rate of 26 % . Corruption was seen as a key problem by 17 % of Spaniards in the government 's main `` CIS '' survey last December , nearly double the rate of the previous month and the highest rate by far since the term `` corruption and fraud '' was included in the poll 11 years ago . Read more : Spanish duke subpoenaed in corruption case . El Pais reported that the money came into Popular Party coffers through secretive donations from construction firms and other businesses , and was used for various purposes , including tens of thousands of dollars in secretive payments to party officials . El Pais reported that the individuals and companies cited in the alleged documents have denied giving or receiving party funds in an off-the-books manner . Read more : How the indignados motivated Spain . A former Popular Party treasurer , Luis Barcenas , is under investigation for an alleged multimillion-dollar account in Switzerland . El Pais headlined its story Thursday : `` The secret papers of Barcenas . '' Another newspaper , ABC , headlined its story : `` Luis Barcenas accuses the Popular Party leadership of having collected in B , '' the letter Spaniards typically mention when referring to secretive payments made in cash , with the aim of avoiding taxes . Dolores de Cospedal , the Popular Party 's secretary general , was critical of the reports on Rajoy . `` The only aim of this alleged information is to hurt the Popular Party , its leaders , and certainly to hurt the prime minister , '' she said . But opposition socialists said there is a quick way to clear up any doubts . Said Alfredo Perez Rubalcaba of the Socialist Party : `` I ask that the prime minister himself makes an appearance to answer two simple questions : Did he collect these payments or not ; and if so , off the books or aboveboard ? '' A separate scandal is affecting Spain 's royal household , where King Juan Carlos ' son-in-law has been a suspect in a fraud case since last year . Read more : Court drops case against Spain 's best-known judge . Inaki Urdangarin , who was granted the title of Duke of Palma when he married the king 's youngest daughter , Princess Cristina , in 1997 , is under investigation for allegedly diverting public funds that were earmarked for his foundation for private use . A judge has ordered Urdangarin and a former business associate , Diego Torrres -- both of whom profess their innocence -- to deposit a joint bond of 8 million euros ( $ 10.8 million ) for potential civil damages . If not , the judge would move to embargo assets of the two men , a court spokeswoman said . And this week , the secretary of Princess Cristina and her sister , Princess Elena , was named as a suspect in the same case . The secretary , Carlos Garcia Revenga , denies any wrongdoing and has been called to testify at a preliminary hearing in late February . The Socialist Party in past years has been hit by corruption scandals involving large sums of money and top officials . Last week , the party forced out the director of a party foundation after allegations that he and his wife received payments for articles written under a pseudonym . The Socialists called on other parties to also come clean when hit by scandals . The Catalan nationalist Convergence and Union coalition , or CiU , the ruling party in the northeastern region of Catalonia , also has seen recent allegations of corruption against current or former leaders , and some of their family members . All of these allegations have also been denied .
Latest scandal involves allegations of payments to Popular Party leaders . December survey shows growing number of Spaniards see corruption as a key problem . Score: 6 Parties named in the scandals have said they 're innocent of the charges against them .