Portugal's former socialist prime minister Jose Socrates has been accused of taking bribes of wine estimated to be worth more than $28 million

Socrates, 60, was arrested in 2014 and spent nine months in jail before being released in 2015 under house arrest.

Portugal said Wednesday it has charged former socialist prime minister Jose Socrates following a three-year corruption probe, which revealed he may have taken bribes of wine worth millions of euros.

The former Portuguese premier was indicted on 31 bribery charges and other crimes, including money laundering, tax fraud and falsification of documents, the general prosecutor's office said in a statement -- a decision that had been expected for several months but was delayed over evidence-gathering.

"The accusation is baseless," lawyers for Socrates said, adding in a statement that they intended to use "all legal means" to defend their client.

In a 4,000-page indictment that also targets 18 other individuals and nine companies, investigators say Socrates and his accomplices accumulated an estimated fortune of more than 24 million euros ($28 million) in Switzerland, in exchange for favours granted to several companies -- including the Espirito Santo bank that went bankrupt in summer 2014 amid accounting irregularities.

The investigation looked at crimes Socrates allegedly committed between 2006 and 2015. He was prime minister from 2005 to 2011.

Socrates, 60, was arrested in 2014 and spent nine months in jail before being released in 2015 under house arrest.

The former political leader has always maintained his innocence.

The indictment also targets businessman Carlos Santos Silva, a childhood friend of Socrates, accused of acting as his intermediary and receiving significant money on his behalf.

The prosecutor's office also formally charged Ricardo Espirito Santo Salgado, the former head of Espirito Santo bank and two former officials of Portugal Telecom.