Former Supreme Court judge David Levine, QC, the Inspector of the ICAC, confirmed late on Monday that he had "initiated what is known as an audit of this inquiry".

The audit requires the ICAC to hand over "all material that it lawfully can provide to me as to its investigation and inquiry", Mr Levine told Fairfax Media.

The audit ratchets up the pressure on the ICAC, which has come under fire from sections of the media and the legal profession since it announced it was investigating the high-profile silk last Thursday.

Mr Levine, who has wide powers to investigate the commission's operations, said this was an "unusual case" and the only information he had at the time he initiated the audit was the ICAC's press release and media reports.

The audit would "not interfere with how ICAC carries out its investigation", he said.

Public hearings in Operation Hale are due to start on Monday, November 10.

At the centre of the inquiry is the allegation that Ms Cunneen and her eldest son, Stephen Wyllie, told his girlfriend, Sophia Tilley, to fake chest pains to avoid being breath-tested after a car crash in May.

Ms Tilley, 25, allegedly took the advice of her 26-year-old boyfriend and Ms Cunneen, who has denied the allegations and said they could "only be the result of a malicious complaint".

All three are being investigated over whether they were trying to pervert the course of justice, an offence punishable by up to 14 years in jail.

Mr Levine said the Commissioner of the ICAC, former Supreme Court judge Megan Latham, had "agreed to co-operate" with the audit.

Asked why he had initiated the audit, Mr Levine said: "I have the power to do so."

He said he had "no present reason to be concerned" when asked if he shared concerns reported in sections of the media.

"There exists, in relation to ICAC, the Police Integrity Commission and the NSW Crime Commission the Office of Inspector whose function it is to oversee how ICAC, PIC and the Crime Commission conducts its inquiries," Mr Levine said.

The inquiry into Ms Cunneen has sparked fierce criticism of the ICAC, with sections of the media labelling the investigation a "witch hunt".

Former Liberal premier Nick Greiner, who set up the ICAC 25 years ago, questioned whether the commission was straying beyond its "core task" in investigating the top prosecutor.

"Its core task is about official conduct and the integrity of official conduct," Mr Greiner said.

"It would appear that what is alleged is about personal conduct."

Under the ICAC Act, "corrupt conduct" includes the conduct of any person, whether or not a public official, that adversely affects, or could adversely affect, the exercise of official functions by a public official.

The act says such conduct "could involve ... perverting the course of justice".

The Inspector of the ICAC has extensive powers to investigate the commission's operations and also deals with complaints.

After an investigation or audit, the inspector can refer matters "to other public authorities or public officials for consideration or action" and, in some cases, could recommend disciplinary action or other proceedings against officers of the commission.

It has been a difficult year for the ICAC. It has attracted criticism as it switched its focus from Labor to Liberal figures in its high-profile investigation into Liberal Party fundraising.

It is also the subject of a parliamentary inquiry into the number of prosecutions arising from its investigations, which may result in a change to its statutory powers.

The ICAC declined to comment.