Protesters jeered the former treasurer of Spain's ruling Popular Party on Wednesday after prosecutors questioned him about documents that allegedly show he once paid slush money to leading party members, including Prime Minister Mariano Rajoy.
A handful of people shouted "thief" and "give the money back" at Luis Barcenas as police escorted him to a waiting taxi.
Barcenas was called in for questions after leading newspaper El Pais last week published what it called Barcenas' "secret papers," with alleged copies of records from several years ago showing names and amounts received. The money was allegedly mostly paid by construction companies.
Both Barcenas and the Popular Party, which have since broken ties, claim the documents are false and deny any wrongdoing.
Barcenas declined to talk to reporters Wednesday.
The scandal, although only one of many in Spain, has particularly angered the public because Rajoy is demanding major sacrifices from Spaniards as the country battles recession and 25 percent unemployment.
Speaking in Germany on Monday, Rajoy said the allegations were "completely false" and vowed that his government would not let the scandal distract his reform course.
Opposition leaders have called for him to resign. Police had to cordon off streets around the party's headquarters for several days in a row last week to prevent protesters getting near.