Prime Minister Mariano Rajoy of Spain has strongly denied media claims that he and other members of the governing Popular Party received secret payments.
"I have never received nor distributed undeclared money," he said, stressing that he would not resign.
El Pais newspaper published photographs of ledgers showing payments to Popular Party figures on Thursday.
It said Mr Rajoy had collected 25,200 euros ($US34,000) per year between 1997 - 2008.
Mr Rajoy and his party were elected by a landslide in November 2011 on a promise to reduce the high public deficit.
Addressing the PP national executive meeting in an extraordinary session in Madrid to discuss the El Pais allegations, Mr Rajoy said:
"It is not true that we received cash that we hid from tax officials."
He added he would publish on the party's website full details of his income and assets.
El Pais said the photographs it had published were of ledgers kept by former treasurers Luis Barcenas and Alvaro Lapuerta between 1990 - 2009.