The NT’s anti-corruption watchdog was forced to end an investigation into “serious” allegations that Labor Government ministers were misled by an unnamed individual, after ICAC Michael Riches was unable to access Cabinet documents, the commissioner disclosed during Estimates hearings on Tuesday.

The current ICAC legislation prevents investigators from accessing Cabinet documents, however, it was unclear why the government would not have waived cabinet confidentiality to facilitate the investigation in the best interests of justice.

Mr Riches did not provide details of the allegations other than to say the person alleged to have misled Cabinet was from “outside of the Cabinet”.

“It’s a matter that in my view was quite a serious matter,” he said.

“It related to an allegation of misleading Cabinet. However, because I’ve not been able to access the Cabinet documents themselves, I simply cannot progress with the investigation because the Cabinet documents themselves are the key to the investigation.”

Mr Riches added that he does not “criticise the government in any way” as they are “entitled to claim public interest immunity in respect of Cabinet documents”.

“Certainly in respect of that investigation, it’s not a decision of mine,” he said. “It’s the Parliament that’s made that decision in respect of the content of the legislation.”

Former chief minister Michael Gunner’s closed-door review of the ICAC Act by hand-picked long-time public servant Greg Shanahan was also raised during Estimates hearings, but current Chief Minister Natasha Fyles indicated its findings would not be released publicly and legislation to amend the Act would be written by the government.

It was unclear if the secret review would explore changes to the legislation to assist the ICAC’s investigations.

Under Section 70 of the ICAC Act, documents related to Cabinet are exempt from being investigated, including what information ministers relied on to make decisions affecting the public.

It is widely used in other jurisdictions to protect politicians from divulging the discussions they have behind closed doors while deliberating on decisions.

However, Mr Riches said he wasn’t interested in the specifics of those discussions in relation to the serious matter he was investigating.

“It wasn’t the cabinet discussions that I was interested in, it was an allegation of misleading by somebody outside of the Cabinet,” he said. “So, look, somewhat different but nevertheless captured by Section 70.”

It was unclear if the allegation was referred anywhere else or to the responsible minister. Mr Riches added that he would not provide any further information about the matter.

“That’s an allegation that’s untested and the bad thing would be to identify individuals involved because whether or not the allegations are true, I just don’t think it would be fair in those circumstances,” he said.

Opposition CLP Leader Lia Finocchiaro then asked Ms Fyles about her role in awarding the $12 million grant to the Darwin Turf Club for the controversial grandstand project and asked about the government’s call on the club to repay the money.

Ms Fyles had the matter pushed to another time.

ICAC’s budget cut as 14 investigations underway

It was also revealed at Estimates that the ICAC’s funding had been cut by 20 per cent – or $1.7 million – and that the government had rejected a recent budget allocation submission Mr Riches had made.

“I am of course disappointed that that is the case,” Mr Riches said.

“The significant reduction from this year’s budget will of course impact the discharge of my statutory functions.”

Ms Finocchiaro said the government’s cut to the ICAC’s budget does not “pass the pub test” and are poor optics given the government is “undoubtedly under investigation”.

Ms Fyles defended the decision to clip the budget and said Mr Riches could apply for a Treasurer’s advance if more funding is needed.

Mr Riches has not yet released a public report involving an investigation since taking office last July.