In an interview with business news channel CNBC, Mahathir said he is willing to declare his assets if requested, but admitted “it would not be easy to trace assets (accumulated) over more than 40 years”.

“They say they are investigating, but the investigation does not involve any demand to declare my assets,” he said.

Last month, MACC confirmed that it was investigating the two-time former prime minister. Chief commissioner Azam Baki later revealed that the investigation was linked to the declaration of assets.

In March, Mahathir’s two eldest sons revealed that MACC ordered them to assist in an investigation into their father.

MACC had also previously ordered Mokhzani, 63, and his brother, Mirzan, 65, to declare their assets dating back to 1981, the year Mahathir became prime minister.

Mokhzani said Mahathir was the “primary suspect” and that the brothers were witnesses to whatever MACC was investigating.

In the interview, Mahathir insisted that he was never involved in corrupt practices during his tenure as prime minister.

“I made sure that even my family could not be involved in government business because I might be accused of nepotism,” he said.

He said Prime Minister Anwar Ibrahim’s claim that he had accumulated billions of ringgit was baseless.

“To date, he has not been able to prove that I have taken a single sen. I have (sued) him in court to provide evidence that I have taken money,” he said.

Last year, Mahathir filed a RM150 million libel suit against Anwar, claiming that Anwar had accused him of enriching himself and his family members as well as being a racist.

He is seeking RM50 million in general damages and an additional RM100 million in exemplary damages.

Mahathir also called on MACC to provide any evidence of an offence he allegedly committed.