The resignation comes at a time when there is a speculation that 94-year-old Mahathir was attempting to form a new ruling coalition that would exclude his promised successor Anwar Ibrahim.
On the other hand, Mahathir's party, the Malaysian United Indigenous Party (Bersatu) announced it would be dropping out of the ruling coalition Pakatan Harapan in support of the prime minister.
"All members of the House of Representatives of the party have signed a statutory declaration to continue supporting and putting their trust in Mahathir Mohamad as the prime minister," Bersatu President Muhyiddin Yassin said in a statement on Monday.
This announcement has fueled speculation that Mahathir is planning to form a new ruling coalition that excludes his designated successor Anwar Ibrahim.
Anwar Ibrahim was designated to take over the reins from interim Prime Minister Mahathir Mohammed as planned and agreed by the coalition.
On 8 January 2018, Mahathir was announced as the Pakatan Harapan opposition alliance's prime ministerial candidate for the election to be held on 9 May 2018, seeking to oust his former ally Najib. Wan Azizah, wife of his former political enemy Anwar, ran as his deputy.
According to the election results disclosed on 10 May 2018, Pakatan Harapan had claimed victory, thus successfully propelling Mahathir to the prime ministerial seat once again. He would then seek a pardon for Anwar, in order to allow him to take over the leadership. (İLKHA)