Madrid (AFP) – Tens of thousands of people rallied Sunday in an opposition-organised demonstration in Madrid accusing the government of Prime Minister Pedro Sanchez of corruption.

Protesters, many waving red and yellow Spanish flags, massed in the Plaza de Espana, a large square in the centre of the Spanish capital, and chanted "Pedro Sanchez, resign!".

"The expiry date on this government passed a long time ago. It's getting tiring," Blanca Requejo, a 46-year-old store manager who wore a Spanish flag drapped over her back, told AFP at the demonstration.

The Popular Party (PP) called the rally after leaked audio recordings allegedly documented a member of the Socialist party, Leire Diez, waging a smear campaign against a police unit that investigated graft allegations against Sanchez’s wife, brother and his former right-hand man.

Diez has denied the allegations, telling reporters on Wednesday that she was conducting research for a book and was not working on behalf of the party or Sanchez. She also resigned from Sanchez's Socialist party.

PP leader Alberto Nunez Feijoo has accused the government of "mafia practices" over the affair, and said Sanchez is "at the centre" of multiple corruption scandals.

"This government has stained everything -- politics, state institutions, the separation of powers," he told the rally, going on to urge Sanchez to call early elections.

The PP estimated that more than 100,000 people attended the rally, held under the slogan "Mafia or Democracy."

The central government’s representative in Madrid put the turnout between 45,000 and 50,000.

The government's spokeswoman, Pilar Alegria, mocked the turnout, writing on X that veteran Spanish rock duo Estopa drew a larger crowd to their recent concert at Madrid's Wanda Metropolitano stadium than "the apocalyptic Feijoo at the Plaza de Espana."

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

He came to power in June 2018 after ousting his PP predecessor, Mariano Rajoy, in a no-confidence vote over a corruption scandals affecting involving the conservative party.

Rafael Redondo, a 73-year-old real estate agent, said the corruption cases that have affected the PP were "completely different".

"The corruption that may have existed in the PP involved individuals acting on their own. But the Socialist Party is a criminal organisation which has committed crimes from A to Z," he told AFP at the rally.

Maria del Mar Tome, a 59-year-old businesswoman, said she had turned up because "we want Pedro Sanchez to go away once and for all, because this man is corrupt, he's a liar."

This is the sixth protest which the PP has organised against the government since Feijoo took the helm of the party in April 2022

The demonstration comes as the PP is gearing up for an extraordinary party congress set for July.

Originally set for 2026, Feijoo moved the event forward, citing the need for the party to "be prepared" in case of early national elections in what was seen as an effort to consolidate his power.

Rajoy and another former PP prime minister, Jose Maria Aznar, attended Sunday's rally, along with several heads of regional governments.

Recent polls show the PP holding only a slim lead over the Socialists. although Sanchez remains the most highly rated party leader among voters.

One in four voters, 24.6 percent, said Sanchez is their favourite party leader to lead the country, ahead of the leader of far-right party Vox, Santiago Abascal, who was picked by 17.1 percent, according to a poll published Monday in daily newspaper El Pais.

Feijoo was the third most popular option, with 16.6 percent.

The next general election is expected in 2027.