Spanish Prime Minister Mariano Rajoy will appear in Congress to give his side of the "Barcenas" corruption case, President of the Congress of Deputies Jesus Posada confirmed on Tuesday.

Rajoy will speak about his alleged involvement in the Barcenas case in which he and some other prominent party members have been accused by former Popular Party (PP) Treasurer Luis Barcenas of receiving illegal cash payment from a slush fund set up in Switzerland with the proceeds of illegal donations to the party.

Rajoy said on Monday that he would appear in Congress at either the end of July or the start of August to speak about the Barcenas case, saying he was doing so out of his own initiative, despite the fact that the opposition had threatened to call for a vote of no confidence this Wednesday should he refuse to give his version of the events.

The prime minister has chosen to speak on the day when the majority of Spaniards who can afford to do so will be starting their summer holidays.

Posada explained that Rajoy will use his appearance to also discuss the economic situation of the country in what looks like a clear attempt to bury the Barcenas case in other news on a day when Madrid is at its most empty.

Meanwhile, because of building work being held on the Congress building, Rajoy will actually speak in the Senate building in a different part of the city.

Unless he is able to provide a satisfying response to the accusations against himself and some others such as PP Secretary General and President of Castilla la Mancha, Maria Dolores de Cospedal, he will come under increasing pressure to resign.

This pressure will obviously come from the opposition, but also from inside his own party as members increasingly view him as a "lame duck" who will increasingly hinder their chances of re-election in the next general election, which is due in 2015.