Dr Mahathir Mohamad's lawyer will write to the Attorney-General's Chambers to enquire about the prime minister's challenge against the Royal Commission of Inquiry's findings on the foreign exchange losses in the 1990s.

Lawyer Mohd Haniff Khatri Abdulla informed Justice Azizah Nawawi that he will write a letter of representation to the AGC next week to seek clarification on the issue, as well as on a number of related cases.

"I met (attorney-general) Tommy Thomas personally on Aug 3 to enquire about this issue, as well as other related cases, and he asked me to formally write to him on the matter," he told reporters outside the Kuala Lumpur High Court.

Today was initially fixed for hearing on the AGC's preliminary objection to Mahathir's challenge.

Haniff said his client's stand was that every document used and transcripts of the proceedings, including all witness testimonies, should be produced in the final RCI report.

He added that the AGC's stand was needed following the change in government after the May 9 general election.

Azizah fixed Sept 18 for him to update the court. Senior federal counsel Mazlifah Ayob appeared for the chambers.

Mahathir, who led opposition pact Pakatan Harapan at the time, filed the originating summons last December against all six members of the forex RCI, claiming that their report was incomplete. 

The forex RCI consisted of Mohd Sidek Hassan, Kamaludin Md Said, Tajuddin Atan, Saw Choon Boon, K Pushpanathan and Yusof Ismail. Then-prime minister Najib Abdul Razak, the cabinet and the government were also named as respondents.

Mahathir sought a declaration that the forex RCI report is invalid, as it does not include all witness testimonies – including written or oral requests in the form of transcripts or video recordings – or submissions made by lawyers.

The related cases cited by Haniff also involving the AGC are Khairuddin Abu Hassan's unlawful detention under the Security Offences (Special Measures) Act 2012, Mahathir's review of the misfeasance in public office suit against Najib, and former Umno member Zahid Md Arip's challenge on the 1MDB report being classified under the Official Secrets Act.