Dr Mahathir Mohamad is no longer credible enough to ask for Prime Minister Najib Abdul Razak to step-down over the 1MDB issue, said Communications and Multimedia Minister Salleh Said Keruak.

"The BMF and forex scandals makes Mahathir the last person in Malaysia qualified and credible enough to ask Najib to step down from office citing 1MDB as the excuse," Salleh wrote on his blog last night.

He was referring to a recent resurgence of reports on financial scandals during Mahathir's time as prime minister.

On Tuesday, declassified reports by the US Central Intelligence Agency (CIA) suggested that Mahathir's government was aware of BMF's dubious dealings in the 1980s.

The BMF scandal had cost US$1 billion in losses due to its lending practices.

Meanwhile, former Bank Negara assistant governor Abdul Murad Khalid yesterday claimed that the central bank had lost US$10 billion in the foreign exchange market during Mahathir's era.

Murad said despite the heavy losses, there was no investigation over the matter.

Mahathir had responded to the BMF allegations by accusing the CIA of conspiring against him.

He also wrote a blog post to point out differences between the BMF and 1MDB scandals, such as that the CIA report on the BMF scandal did not implicate the prime minister.

Salleh however said the CIA report clearly showed that Mahathir was responsible for BMF's losses.

He also drew his own comparisons between BMF and 1MDB, saying the latter was a victim of sabotage.

"The truth is 1MDB was sabotaged to turn it into a problem and it started with the sabotage of the initial public offering (IPO)," he said.

The government has blamed the opposition's attacks on 1MDB for derailing the IPO of then-1MDB subsidiary Edra Global Energy, which in turn torpedoed efforts to pay off the state investment firm's debts.