Former premier Dr Mahathir Mohamad has welcomed calls for a royal commission of inquiry (RCI) into the BMF and forex scandals.

"They are welcomed to do so (set up an RCI) but we want the same kind of commission into the RM2.6 billion that went into Prime Minister Najib Abdul Razak's accounts and also what happened to 1MDB," Mahathir said at a press conference in Petaling Jaya today.

His former adversary turned ally, DAP stalwart Lim Kit Siang voiced similar opinions.

"I have called for an RCI into BMF and the Bank Negara forex dealings and I stand by that.

"But what is more important now is 1MDB," Lim said.

He also said that Najib, who was defence minister in 1991, was also responsible for the scandals under the principle of collective responsibility.

"If there is any criminality, he (Najib) should be in the dock," Lim said.

The duo were responding to calls from Umno Youth and PAS Youth for a probe into the Mahathir-era scandals.

While standing by his own calls for a probe, Lim questioned why the two youth wings were looking to the past instead of calling for a more urgent probe into the 1MDB scandal.

Lim then became visibly agitated and lost his cool when asked if he would be speaking about the BMF and forex scandals differently if Mahathir was not his ally now.

"How have I said it differently? How? You can't substantiate it, you are making a baseless allegation.

"You prove it! If not you are making a baseless allegation," Lim said.

The crowd at Zaid's home then jeered when the journalist told Lim that he was from TV3.

"TV3 is a maker of false news... TV3 should provide genuine news," Lim said, not allowing the journalist to explain himself.

Lim had written two books about the scandals.

The Mahathir-era scandals re-entered the spotlight after the US Central Intelligence Agency (CIA) declassified a report on BMF recently.

The report 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 had claimed 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.

Meanwhile, 1MDB is the focus of multiple investigations overseas.

The US Department of Justice (DOJ) claimed that more than US$3.5 billion in 1MDB funds had been misappropriated.

This included allegations that US$731 million made its way into the accounts of Malaysian Official 1 (MO1).

Minister in the Prime Minister's Department Abdul Rahman Dahlan had confirmed that Najib is MO1.

Najib, however, denied having misappropriated public funds.

Najib and attorney-general Mohamed Apandi Ali had said that the "RM2.6 billion" in the premier's accounts prior to the 2013 elections was a donation from the Saudi Royal family.