Leire Díez: The latest chapter in the corruption saga affecting Spain's PM

A former member of Spanish Prime Minister Pedro Sánchez's Socialist party on Wednesday denied waging a smear campaign against a police unit investigating corruption accusations targeting members of his inner circle.

Leire Díez has come under scrutiny after leaked audio records surfaced of her talks with a police commander and a businessman implicated in corruption probes.

In the recordings, she appears to offer judicial leniency to both in exchange for potentially compromising information on top members of the Guardia Civil police force's anti-corruption unit.

This unit is investigating graft allegations levelled against Sánchez's wife, brother and his former right-hand man, prompting allegations that she may have been trying to interfere with these probes.

But Díez attempted to quash the growing scandal, telling reporters on Wednesday that she was conducting research for a book and was not working on behalf of the party or Sánchez.

"I am not a woman in the shadows. I have been doing investigative work for years," she said a day after she resigned from the party.

She also lashed out at what she called "calculated and fabricated leaks".

Tensions flared at the press conference when businessman Victor de Aldama, a central figure in one of the corruption cases troubling Sánchez's administration, unexpectedly attempted to confront Díez.

"She lies and mocks everyone," he shouted.

The main opposition Popular Party (PP) has called for a protest in Madrid on Sunday against the government over the affair, accusing it of "mafia practices".

The PP, as well as far-left party Podemos and Catalan pro-independence party ERC, have demanded that the prime minister appear in parliament to give explanations over the case.

Sánchez has dismissed the probes affecting members of his inner circle as part of a "smear campaign" carried out by the right wing to undermine his government.