Crown prosecutor Margaret Cunneen has criticised the powers of the Independent Commission Against Corruption as "extraordinarily draconian" after a decision by NSW authorities not to charge her over allegations she had tried to pervert the course of justice.

Two days after the decision to not prosecute her over allegations she advised her son Steven Wyllie's girlfriend, Sophia Tilley, to fake chest pains to avoid a breath test after a car accident the couple was involved in last year, Ms Cunneen blasted ICAC for the quality of its investigation.

"Even the most elementary investigative step of speaking to any of the kind bystanders who helped Sophia from the wreckage would have revealed that she was being treated in the ambulance before the police arrived," Ms Cunneen told Fairfax Media.

"She didn't say a word to the police at the scene so she certainly didn't tell them any lies. She was taken to hospital and routinely blood-tested with a 0.00 result."

Ms Cunneen - who has always strenuously denied the allegation - said it "was always an impossibility on its facts".

It was "a dreadful thing that this young couple, and Sophia in particular, having just survived a devastating crash in which she was not at fault, would be subjected to the extraordinarily draconian powers of ICAC which extend way beyond those of the Police or the proper courts."

As part of its investigation ICAC last year issued warrants to seize the mobile phones of Mr Wyllie, Ms Tilley and Ms Cunneen. The trio was also called to give evidence to the commission in private hearings.

"These powers should be reposed in only competent and scrupulously impartial hands and reserved for the most serious of criminal matters," Ms Cunneen said on Sunday.

Later, speaking on radio 2GB, Ms Cunneen said that "if this could happen to me ... then it can happen to any citizen and any family".

"I'm fortunate, I know a bit about the law and hundreds if not thousands of lawyers, many of whom have been of assistance to me," she said.

"But if this happened to any other family without those resources, they'd just have to cop it".

The ICAC had referred evidence to the NSW Director of Public Prosecutions relating to the allegation against Ms Cunneen.

The referral followed a successful High Court challenge by Ms Cunneen against ICAC proceeding with public hearings into the matter. The court found ICAC was acting outside its powers in investigating Ms Cunneen.

Given Ms Cunneen's role in the NSW legal profession, the NSW DPP asked the Victorian Chief Crown Prosecutor to advise on the matter.

On Friday, NSW Solicitor-General Michael Sexton said he had considered the advice of the Victorian Chief Crown Prosecutor in forming the view no prosecution should be brought.

The ICAC has declined to comment on the decision, which comes as former chief justice of Australia Murray Gleeson and senior barrister Bruce McClintock prepare to hand their review of ICAC's powers to Premier Mike Baird on Friday.

The review was commissioned by Mr Baird following the High Court decision which found ICAC did not have the power to investigate Ms Cunneen.