Umno leaders who are "sulking" (merajuk) and distancing themselves from the party should return to the fold to ensure BN's victory in the upcoming by-elections, a division leader said.

Cheras Umno chief Syed Ali Alhabshee said these included Umno leaders who were upset with party president Najib Abdul Razak.

"If they really love Umno and have no personal agenda, come back and combine forces to topple the opposition, prove your sincerity and loyalty to the party," he said in a blog post today.

While he did not mention any names, he is likely referring to Umno bigwigs such as suspended deputy president Muhyiddin Yassin and former Kedah menteri besar Mukhriz Mahathir.

The duo are now part of a campaign spearheaded by former premier Dr Mahathir Mohamad to topple Najib.

Syed Ali said the Sungai Besar and Kuala Kangsar by-elections would be a litmus test as to how united Umno is, and how ready the party and BN are to face the 14th general election.

"The by-elections will be the measuring stick to see how much voters support Umno, taking into account the current political scenario," he wrote.

He believes that Umno will win big in both Kuala Kangsar and Sungai Besar but cautioned that the party machinery should not be lulled into a false sense of security.

The twin by-elections are expected to see three-cornered fights among Pakatan Harapan, PAS and BN.

The June 18 parliamentary polls were triggered by the deaths of its incumbents in the recent Sarawak helicopter tragedy.