KUALA LUMPUR - The spat between former Malaysian prime ministers Muhyiddin Yassin and Najib Razak is escalating as election fever grips Johor.

Tan Sri Muhyiddin, who leads Parti Pribumi Bersatu Malaysia (Bersatu), on Thursday said he would be "ashamed" to be associated with Umno, a party with a "boss" who has been convicted in the courts.

"There is a blessing when Bersatu does not work with Umno as Bersatu won't become entangled in the moral problems plaguing Umno leaders.

"Personally, I'd be ashamed to be associated with a party that embraces someone who has been convicted by the courts of a serious crime, as a boss," Mr Muhyiddin said in a statement, in a clear reference to Umno's ex-president Najib.

Mr Muhyiddin is head of Bersatu and the Perikatan Nasional (PN) alliance. PN is part of Malaysia's governing coalition led by Umno.

But there are tensions now between the organisations, as Umno has now refused to work with PN and Bersatu as electoral partners.

They will instead be facing off in the Johor elections.

Malaysia's Court of Appeal in December upheld Najib's conviction on graft charges relating to RM42 million (S$13.6 million) he received from SRC International, a former unit of state fund 1MDB. But he is out on bail and free to move about, while appealing his case to the Supreme Court.

The Johor polls must be held within 60 days after the state assembly was dissolved on Jan 20.

On Friday (Feb 4), Mr Muhyiddin told Najib to focus on bringing stability to the country instead of raising past issues, such as involving the previous Sabah state election, The Star newspaper reported on Saturday (Feb 5).

Referring to Najib's attacks on Mr Muhyiddin on the Sabah state election, which was held on Sept 2020, Mr Muhyiddin said: "I find it weird and amazing that a former prime minister like him can continue raising issues that have been resolved."

"The Sabah government has already been formed and is working very well with good cooperation and understanding.

"I don't know what else he wants to dig up, and don't know what are his tricks and motivation" he told reporters.

Mr Muhyiddin was asked about Najib's accusations that he tried to undermine Umno-led Barisan Nasional during the 2020 Sabah polls.

Najib charged that Mr Muhyiddin had planned to name Sabah Bersatu chief Hajiji Noor as Sabah chief minister candidate all along, refuting Mr Muhyiddin's Facebook post on Thursday.

In the post, Mr Muhyiddin claimed that he named Datuk Seri Hajiji as the candidate for the position only because despite him asking Umno president Zahid Hamidi to submit a name, the latter did so only at the end of the campaign period.

Najib said in a Facebook posting on Thursday (Feb 3) that Mr Muhyiddin and Bersatu had been planning to destroy Umno by poaching its members.

"Why does Umno have to be friends with a party whose actual intention is to end Umno forever with a plan from the beginning to bribe and buy Umno members?" he said.

Last month, Najib attacked Mr Muhyiddin by saying the emergency proclamation that lasted nearly eight months when Mr Muhyiddin was prime minister was not successful in curbing Covid-19 and protecting the economy.

Meanwhile, Zahid said the party machinery has to use social media as its main platform to reach out to voters in the upcoming election.

He also reminded party members to work with each other because voters wanted a quick response to issues raised when launching a party event on Friday.