Prime Minister Mariano Rajoy and PP secretary general María Dolores de Cospedal at the start of Monday's National Executive party meeting. Ballesteros / EFE

A former Popular Party (PP) lawmaker has come forward to acknowledge the practice of payments to the conservative organization's leaders -- sometimes "given in cash-stuffed envelopes" -- which supports allegations in the press that PP treasurers had set up a secret slush fund used to hand out bonuses to top officials.

Jorge Trías Sagnier, who served in Congress from 1996-2000, wrote in an EL PAÍS column published in the Spanish edition on Monday that Prime Minister Mariano Rajoy and PP secretary general María Dolores de Cospedal need to offer the public explanations about the party's financing, even though they both put an end to this practice. Trías Sagnier is the first PP representative, past or present, to publicly admit that such practices existed in the party.

In the article, Trías Sagnier writes: “Now the PP, and especially its ex-treasurer, Luis Bárcenas – with whom I have trekked through mountains, had long conversations and whose friendship I will not renounce, whatever his future may be – are faced with understandable scrutiny. They must, then, clarify and explain the system of financing so that we can believe in them. And the opposition – all of its members and the Socialists in particular – must state publicly if they have also made use of these bad practices.”

"If there isn't much faith placed in those who are governing this nation, how can they demand the sacrifices they are asking citizens to make?" Trías Sagnier concludes.