PETALING JAYA - The opposition Pakatan Harapan alliance in Selangor state is threatening to unravel less than a month before a by-election, raising doubts over the unity of Malaysia's opposition.

Selangor Mentri Besar Datuk Seri Azmin Ali, who is also deputy president of Parti Keadilan Rakyat (PKR), on Wednesday (May 18) issued an ultimatum to three state executive councillors with Parti Islam SeMalaysia (PAS) to resign by Monday if their party insists on contesting for one of the seats up for grabs in the June 10 by-election, The Star reported on Thursday.

Datuk Seri Azmin wants PKR to contest the seat instead of PAS, which has fallen out with PKR and another opposition camp partner Democratic Action Party (DAP), or Parti Amanah Nasional, a PAS splinter, the report said.

Two constituencies, Sungai Besar and Kuala Kangsar, will be electing new MPs after the original incumbents, from the ruling Umno, were killed in a helicopter crash while campaigning in Sarawak state elections earlier this month.

Azmin told the PAS councillors that PKR would have a better chance against Umno in Sungai Besar, The Star said.

He said PKR would be able to win Malay and Chinese votes whereas PAS and Amanah would cancel out each other and give an easy victory to Umno.

However, Selangor PAS sources told The Star the party has decided to go ahead with the contest after a late night meeting at PAS president Hadi Awang's house in Rusila, Terengganu.

The three Selangor exco members and several state PAS leaders had flown to Terengganu on Wednesday for the emergency meeting.

"Our president is standing by the central committee decision to contest the by-elections," said the Selangor PAS source according to The Star.

Hadi instructed the exco trio not to resign. He said the party is prepared to be expelled from the government.

Hadi had reportedly said during the meeting that the party "would rather herd the cows of Umno than herd the pigs of DAP".