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.

"He (Mahathir) should be given space to help expand the net of the people's movement. Harapan's structure can't be equated to that of BN's," Anwar said in a statement today.

Various quarters including former Pakatan Rakyat allies Parti Sosialis Malaysia (PSM), and Anwar's hardcore supporters in the Otai Reformasi group, have voiced their displeasure with Mahathir's presence among the opposition.

Anwar, however, said he personally welcomed Mahathir's willingness to join the opposition's struggle.

"Personal sufferings and wounds suffered pale in comparison to the interest of the rakyat and the country's future.

"Tun (Mahathir) is now forced to struggle in a different platform and stressful environment, and he has been quick to adapt and shown courage," the jailed former opposition leader said.

Nonetheless, he said activists and NGOs have a right to monitor and criticise Harapan's progress and put forth suggestions.

He also stressed that the Harapan coalition's goals are to right the wrongs of the current BN regime, including eradicating corruption and abuse of power.