Dr McGirr this week co-signed a letter with NSW Parliament's two other independent MPs that called for the Independent Commission Against Corruption to no longer be subject to annual funding decisions.

Dr McGirr told The Daily Advertiser that ICAC was one of four integrity agencies that were "vital for NSW" as "watchdogs to ensure there is integrity".

"After a report by the Auditor General Margaret Crawford identified several areas of ambiguity that highlighted threats to the independence of these agencies, my fellow independent colleagues Greg Piper and Alex Greenwich and I decided to take the issue directly to Premier Gladys Berejiklian," Dr McGirr said.

"These agencies shouldn't have to go, cap-in-hand, to the government each year to seek funding, especially when and if their work involves investigation of the government and parliamentarians."

Ruth McColl was appointed as Assistant Commissioner for ICAC's inquiry into allegations against former Wagga MP Daryl Maguire reportedly to avoid a conflict of interest with Ms Berejiklian, who had authorised ICAC's funding and was also due to appear as a witness.

Dr McGirr's co-signed letter to Ms Berejiklian referenced a report from the Audit Office of NSW that stated "the current approach to determining annual funding for the integrity agencies presents threats to their independent status".

The letter to Ms Berejiklian stated this report "sets the challenge for your government to address what should have been the situation for funding such organisations as part of their establishment".

"If nothing else, the general public could perceive that the lack of independence and surety of funding for such bodies poses an implied threat or risk to funding of the agencies," the letter stated.

Shooters, Fishers and Farmers Party Murray MP Helen Dalton has also called for ICAC's funding decisions to be independent of the government.

The Department of Premier and Cabinet, in response to a demand from Parliament, provided a letter on Thursday stating that it could not find any record of Mr Maguire declaring his interest in business activities that were mentioned during ICAC's public hearings.

Ms Berejiklian told ICAC this month that she knew Mr Maguire had interests and "assumed that any disclosures were made" but she would "not have hesitated" to report known wrongdoing.