PAS' decision to forge a third force in Malaysian politics will ultimately dilute votes from the Malay community and hand Umno victory, said Dr Mahathir Mohamad.
"Regardless of whether PAS works with Umno or not, PAS will reduce Pakatan Harapan's (potential number of) votes as well as their own votes.
"Harapan and PAS will lose and BN will win. This is PAS' struggle. It is not for race and religion.
"Their purpose is to weaken the Malays," wrote Mahathir on his blog today.
The former premier said history has shown that PAS performs poorly at the polls whenever they go it alone and conversely, do relatively well if they have strong allies.
But this fact was unlikely to sway PAS members, because of their "fanaticism" for their party and their leaders.
"They believe in baiah (loyalty agreement) towards the party and their leaders. This baiah binds them to the point that they would put aside Islam and the Quran.
"The Quran forbids Muslims from allying with evildoers and encourages alliances only for amar ma'ruf (enjoining good). (This concept) is lost on PAS and their leaders.
"Now PAS claims they will fight Umno, but the truth is they will aid Umno's victory. Whether dedak (animal feed) was involved or not, God knows," said Mahathir.
Who's the 'kafir' now?
Mahathir said that it was up to PAS members to decide whether they are going to follow the true teachings of Islam, or continue their baiah and "fanaticism" towards the party and their leaders, whose objective was to fulfil their own "worldly desires".
Meanwhile, Mahathir pointed out that PAS had a habit of "mengkafirkan" (apostatising) their rivals.
He said that since 1959, PAS had declared Umno, MCA, MIC and DAP as "infidels" on multiple occasions, yet forged ties with them at one point or another.
Mahathir said that this was against Islamic practices, because the Quran forbids Muslims from declaring other Muslims as "kafir" (infidels).
"When PAS was allied with the 'kafir DAP' and other infidels (in the past), therefore, in accordance with PAS' version of Islam, then PAS members are themselves kafir.
"But going through the facts of history will not change the minds of PAS members. They are so fanatical over their leaders and party," he added.
PAS was once part of the Pakatan Rakyat coalition with PKR and DAP. Since 2015, the party has broken ties with both parties and intends to face their former allies during the next election.- Mkini