Former prime minister Dr Mahathir Mohamad may be committing sedition or treachery by calling for 'out of the box' methods to remove Prime Minister Najib Abdul Razak, Deputy Home Minister Nur Jazlan Mohamed said today.

"He's saying to the public that he's 'going outside the box, beyond the constitution'.

"Isn't this country governed by the constitution? You have to abide by the constitution.

"What he is advocating can be considered seditious, treacherous," Nur Jazlan told reporters in the lobby of Parliament.

Yesterday, Mahathir called on the Malay Rulers to pressure Najib to step down, but admitted that under the Federal Constitution, the Yang di-Pertuan Agong does not have the power to sack the prime minister.

'Police already investigating Mahathir'

Nur Jazlan said police were already investigating Mahathir and action would be taken if the former prime minister had broken the law.

"The more he talks, the more items are there for the police to investigate. If it results in proof that he contravened the law, then we will take action."

However, he said, as Mahathir's Save Malaysia movement is not getting traction with the public, the government is, at the moment, treating it as a political stunt.

The Save Malaysia movement consists of Umno rebels and leaders from opposition political parties and civil society.

Some leaders are currently embarking on a roadshow to whip up public support and to get more signatories for the Citizens' Declaration, which seeks to pressure Najib to resign as prime minister and implement institutional reforms.