Muhammad, popularly known as Mat Taib, yesterday handed in his membership application form to Pas president Datuk Seri Abdul Hadi Awang at the party headquarters.
His decision has been described as an act of someone who acted out of frustration because his wish for a family member to be listed as a Barisan Nasional candidate in the 13th General Election was unfulfilled.
Malacca Chief Minister Datuk Seri Mohd Ali Rustam said as a party veteran, Mat Taib should have known better than to join Pas.
"From what I heard, he was upset because he had wanted a close family member to contest on BN's ticket in this election.
"He should not put his self interest before the party... this is not the way," he said, adding that Pas must be desperate to have accepted Mat Taib's application.
In Alor Star, Kedah Umno liaison committee deputy chairman Datuk Mukhriz Mahathir said Mat Taib was an ungrateful person who probably thinks that all his worldly sins would be absolved by Pas.
Mukhriz said the question now was whether the former Umno vice-president had forgiven Pas for all the accusations its leaders had hurled at him when he was Selangor menteri besar and a minister.
"Anyway, his defection to Pas will not harm BN's chances of a major victory in this general election."