The police will investigate Xavier Justo's claim that its officers had coerced the 1MDB whistleblower into giving a statement in Bangkok three years ago, said inspector-general of police Mohamad Fuzi Harun.

This included the former PetroSaudi executive's allegation that the police had forced him to say that Najib Abdul Razak was the "best prime minister".

"We will look into all Justo's claims.

"I am aware that this might be related to the recording of his statement in Bangkok (in 2015). We will look into it," Fuzi said during a press conference after launching an anti-corruption seminar at the Royal Malaysian Police College in Cheras this morning.

Yesterday, the Malay Mail quoted Justo as claiming that police officers including Amar Singh, who is now the director of the Commercial Crime Investigation Department, had coerced him when they came to question him over the 1MDB scandal.

He said the police team came with 55 questions, and that they had allegedly coerced him into giving the answers they wanted.

He reportedly told a conference on financial crime in Kuala Lumpur that he was under the impression the admission would help facilitate his release.

Amar had since denied the allegation, saying that such a question about Najib would have been "irrelevant" to the investigation.

When asked for his take on Justo's allegations, and whether Justo had sensationalised his claims, Fuzi replied, "We have to rectify what was his (Justo's) aim, and what he meant.

"We will then look into the matter in detail."

Justo was jailed for three years in Bangkok beginning August 2015, after Thai police said he admitted to blackmail and attempted extortion of former employer PetroSaudi.

PetroSaudi was 1MDB's former joint venture partner.