Spanish Prime Minister Mariano Rajoy pledged here Saturday not to "waver" if irregularities are found to have occurred within his conservative Popular Party.

In a speech at a PP gathering in this southern city, Rajoy described as "a regrettable controversy" revelations that the party's former treasurer, ex-Sen. Luis Barcenas, held large sums in Swiss bank accounts and reports that Barcenas made under-the-table salary payments to PP leaders, an allegation the party's top officials deny.

Rajoy said the party "also has responded rigorously and transparently when it has come under question" and always has acted "decisively" in the face of "irregular behavior."

"If at any time I learn of irregularities or improper conduct, I won't waver because I know it's one of my responsibilities," the premier and PP chairman said.

Clearly alluding to Barcenas, who stepped down from his post in 2009 and formally resigned a year later, Rajoy said "there are people who held some responsibilities and who now are no longer in the party" because the PP held people accountable.

Revelations about up to 22 million euros ($29.3 million) held in Swiss bank accounts by Barcenas, implicated in an ongoing political corruption scandal known as the "Gürtel case," erupted this week.

The controversy heated up further when El Mundo reported Thursday that Barcenas used ill-gotten funds to pay up to 15,000 euros a month in supplementary, undeclared salary payments to PP leaders.

The Gürtel case involving alleged kickbacks from businesses that had been awarded government contracts, influence-peddling and money laundering implicating top PP officials came to light four years ago as a result of an investigation by crusading Judge Baltasar Garzon.

Last February, Spain's Supreme Court convicted Garzon of illegally ordering wiretaps to monitor conversations between several defendants in the Gürtel case and their attorneys and barred him from the judiciary for 11 years.

The allegations of illegal kickbacks and under-the-table payments to PP officials come at a time when Spain is mired in a double-dip recession and the unemployment rate is over 26 percent. EFE