In an open letter to Umno branch members, former prime minister Dr Mahathir Mohamad has called on those who still hold true to the Malay party's original struggle to help him oust Prime Minister Najib Abdul Razak from power.

"I invite Umno members who still adhere to the party's original struggle to help me save the party and the nation. Table no-confidence motions against Najib as party president and PM at all the branch meetings. Move also that the party polls not be postponed and be held this year," Mahathir said in the letter.

Mahathir said they can no longer wait until the 14th general election because by that time Umno led by Najib would certainly lose and once lost, it can never again be re-built.

In his letter, Mahathir said that he is not turning against Umno but he is only against Najib and his nominees in the party who are ruining the party and the nation with their scandals, gross abuses and hard-line approach to critics.

"Najib's rule is cruel. Those that try to advise him are expelled, stripped of their posts, or arrested and hauled to court. New laws are enacted to give power to the government led by Najib to detain anyone without trial.

"Because of this, I left the party led by Najib and as a citizen of this beloved country, I heed the rakyat's call for something to be done to return just rule to the land," said the former prime minister.

Mahathir left Umno for the second time recently to protest what he claimed is the notorious rule by his once hand-picked successor Najib.

He has vowed to bring down Najib from power as he believes that Najib is the source of all evils that plaque Umno and Malaysia.

The doctor's strategy may be to trigger an avalanche of no-confidence motions from the branches, which will ultimately spill over to the division level and if enough of them made it, then the motion might even be tabled at this year's general assembly.

So far, Najib seems to have a strong grip over the divisions which may be a stumbling block to Mahathir's plan.

Najib had postponed the Umno elections purportedly to ensure party unity in the run-up to the next general election, though critics believe that this is because he feared losing his grip on power.

If Mahathir's plan – tabling no-confidence motions and reinstating party polls – makes it to the next general assembly, it may pose a big challenge to Najib.

But as things stand, it is highly unlikely that the motions will get past the divisions.