“I continue to collaborate with justice," Salgado told journalists on leaving the Central Court of Criminal Instruction (TCIC) in Lisbon late on Wednesday after his first interrogation by the judge overseeing the investigation, Carlos Alexandre, who decided to bar him from leaving the country or contacting other suspects in the case. He had, he stressed, "always been available to collaborate with justice from the first day".

Asked by journalists whether he was surprised at being called in for questioning, Salgado said: "I was surprised, but of course that's how it is. Justice has the right to investigate everything and we are here to correspond."

In a statement sent to Lusa, the attorney-general's office said that Salgado had been declared a person of interest in the case, and that he is suspected of acts that might be linked to the crimes of bribery, breach of trust, influence peddling, money laundering and serious tax fraud. The judge opted to bar him from travelling abroad without prior authorisation and from contacting other suspects in the case as well as some people and entities with links to the Espírito Santo group.

Prosecutors had questioned Salgado earlier in the day, before requesting that the judge do the same, with a view to considering limiting his movements.

The main suspect in Operation Marquês is José Sócrates, a former prime minister of Portugal, but there are a further 19, of whom 14 are individuals - including a former minister of Sócrates, his former chauffer, and a businessman who is a close fried.

More than two years after it started, with the first detentions made in November of 2014, the investigation is to be concluded this coming March.

Salgado is also a suspect in two other ongoing criminal investigations.