Former deputy prime minister Musa Hitam believes there are three ways Malaysians can get rid of Prime Minister Najib Abdul Razak.

"The first is through Umno, which is near impossible," Musa wrote in his latest book titled 'Frankly Speaking'.

Pundits have said that Najib is secured in Umno following his purge of party rebels like his former deputy Muhyiddin Yassin, and will remain the party's leader until its own political survival is threatened.

The second method to get rid of Najib, Musa posited, can be through foreign intervention.

"This seems to be the route the 'movement' (Save Malaysia) is pursuing against past negative declarations of anti-foreign meddling.

"This option has possibilities, even if remotely."

It's not clear what sort of plan Musa is referring to, but Mahathir was previously quoted by The Australian as saying that Malaysia now has to "allow foreign interference in our domestic affairs" because all avenues of redress in the country have been closed.

Mahathir, however, denied that he called for foreign intervention.

As for the third option, Musa said this is to let Malaysians decide for themselves whether or not they want Najib out, through the next general election.

The prime minister has been under pressure to quit office due to various scandals, the latest of which are the US Department of Justice's claims that more than US$3.5 billion had been siphoned from 1MDB.

It also named a 'Malaysian Official 1' of having profited from the firm, and the opposition has pointed the finger at Najib.

He has denied abusing public funds for personal gain and blamed such allegations on those conspiring to topple him from power.

Attorney-general Mohamed Apandi Ali had also cleared the prime minister of any wrongdoing.

Musa further revealed in his book that when 1MDB issue first surfaced he had called for Najib to go on leave.

"Around a week after that, in a phone conversation, Najib somewhat teased me by saying, 'I am still not on leave'," he said.