1MDB president and executive director Arul Kanda may have indicated that it was not for Dr Mahathir Mohamad to determine whether he lied about the company, but the former premier said this was self-evident among the public.

"Everybody knows he lied. He said he saw (US$1 billion) cash. Can you imagine seeing US$1 billion there? I will faint.

"I saw that and he assured that (there was cash) and now we find they (1MDB) didn't see anything at all," he said

The former premier was referring to Arul's initial assurance that 1MDB's investment in the Cayman Islands had been fully redeemed in cash and is parked in Singapore.

However, it was later revealed the funds in Singapore was in the form of " units " instead of cash.

Mahathir had earlier this week accused Arul of lying , casting doubt on his credibility to explain 1MDB issues.

However, Arul rebutted that only experts should determine whether he lied or not.

'Professional manner'

"As a professional, I am fully accountable for my actions and am answerable to the 1MDB Board, and our shareholder the ministry of finance.

“In the current context, this also includes the auditor-general, Bank Negara and the Public Accounts Committee.

“These are the lawful authorities to verify whether or not I have ever lied, as has been claimed, as they have access to all information.

“I shall continue to conduct my duties in a professional manner and furnish all information to assist the lawful authorities to verify the truth about 1MDB," he had said.

Mahathir also reiterated that BN will lose the next general election under Najib's leadership.

Asked if Mahathir will ever stop his attacks against Najib, he replied: "Not as long as Najib is prime minister".