A referendum against Prime Minister Najib Abdul Razak could open the floodgates to other referenda, including by states that want to exit Malaysia, Communications and Multimedia Minister Salleh Said Keruak said.

Salleh said Malaysia does not practice a referendum system, and any such call for one on Najib's position as PM must be preceeded by the passing of such a law by Parliament.

"Should Parliament now be asked to pass a new law to adopt the referendum system and make it constitutionally binding?

"What if Sabah and Sarawak, or maybe even Penang, decide to take advantage of this new law and hold a refendum whether to leave Malaysia?

"And what if the majority vote to leave Malaysia? Will it be legally binding?" the Sabah native asked in a statement.

He added that even if a referendum is called on Najib, a legally-binding one would not be conducted by a foreign polling agent but by the Election Commission.

Salleh was responding to former premier Dr Mahathir Mohamad who today said the one thing which could convince the public that Najib should remain as PM is a referendum.

"The referendum should be conducted by a reliable foreign public opinion company, overseen by representatives of the two people concerned.

"If I get more votes, it means the rakyat accepts what I have highlighted about Najib’s financial wrongdoings as true, then he should resign," Mahathir said today.

Condemning the ex-PM, Salleh said the 90-year-old Mahathir "no longer seems to be following the plot and his comments now lack coherency".

He said the formation of a government and the appointment of a prime minister is not a "popularity contest".

The authorities had previously warned Sabah and Sarawak groups agitating for secession that their actions are seditious.

Secession proponents argue that Putrajaya is not honouring the 20-point Malaysia Agreement, to the detriment of the Borneo territories.

They also argue that the states lack infrastructure and development compared to peninsular states, despite being rich in resources as most of the proceeds go to the national coffers.

Sabah, Sarawak, Malaya and Singapore merged to form Malaysia in 1963, but Singapore left the federation in 1965.