KUALA LUMPUR - Prime Minister Muhyiddin Yassin has defended the removal of former premier Mahathir Mohamad and four other lawmakers from Parti Pribumi Bersatu Malaysia, saying that their actions had breached the party Constitution.

"They were not sacked from the party. Their actions had breached the party Constitution, causing their membership to end immediately," said Mr Muhyiddin, who is Bersatu president and had co-founded the party with Tun Dr Mahathir in 2016.

"Tun and his supporters have chosen to continue to work with Pakatan Harapan even though the party has decided against it. If that is Tun's choice, I wish him good luck."

He also said many had urged him to take action against the five earlier.

"I am confident and believe that Bersatu will remain strong. We have faced many challenges from when I first founded this party."

Termination letters from party executive secretary Suhaimi Yahya on Friday (May 29) to the five MPs, including Dr Mahathir's son Mukhriz, informed them that their membership in Bersatu had ended after they sat in the opposition bloc during the last Parliament sitting on May 18.

The Bersatu Constitution states that members who join other parties would be automatically ejected, without the need to be sacked via a disciplinary process.

Dr Mahathir, who was chairman of the party, had refused to support Mr Muhyiddin's move to lead Bersatu out of the Pakatan Harapan (PH) government in February to join forces with then-opposition Umno and Parti Islam SeMalaysia.

Dr Mahathir lost the majority needed to remain as premier, leading to the collapse of the PH government, just 21 months after its historic defeat of Umno in the 2018 general election.

After a week-long political crisis, Mr Muhyiddin was sworn in as Prime Minister on March 1.

Dr Mahathir on Friday slammed the decision to remove him and his supporters, saying that they had done nothing wrong.

"There is no provision in the Constitution regarding where I sit (in Parliament). I have done nothing against the Constitution so that does not mean I have left the party. I can sit anywhere in Parliament."

"Where you sit is not a cause for sacking," he said.