Pakatan Harapan de facto leader Anwar Ibrahim has defended his former arch-nemesis Dr Mahathir Mohamad against critics, who include Anwar's most hardcore supporters.

While he welcomed the criticism and feedback, Anwar dismissed concerns that the coalition would be steered off-course by Mahathir, who is Harapan and Bersatu chairperson.

"Fears about the possibility that a party chairperson can veer from the course which has been agreed upon is not possible in the existing (leadership) structure...