A top New South Wales prosecutor and her son are to face the Independent Commission Against Corruption (ICAC) accused of trying to pervert the course of justice at the scene of a car accident.

NSW Deputy Crown Prosecutor Margaret Cunneen SC denied the allegations, but agreed to step aside while ICAC's Operation Hale investigates the claims against her and Stephen Wyllie.

It is alleged the pair advised Sophia Tilley, who is believed to have been a friend of Mr Wyllie, to pretend to have chest pains at the scene of a car crash on May 31.

Ms Tilley has been accused by ICAC investigators of pretending to have chest pains to stop police getting evidence about her blood-alcohol level.

Ms Cunneen has rejected the claims against her.

"I deny the allegations, which can only be the result of a malicious complaint," she said in a statement.

Attorney-General Brad Hazzard said Ms Cunneen would not have any active involvement in current prosecutions until the ICAC allegations were dealt with.

"Following the announcement today that the ICAC will hold a public inquiry into allegations concerning the conduct of Margaret Cunneen SC and Stephen Wyllie, I have discussed with the Director of Public Prosecutions the issue of Ms Cunneen's involvement in continuing current or future prosecutions," he said.

"The Director of Public Prosecutions has advised me that in discussions with Ms Cunneen SC she has agreed that it is appropriate for her to stand aside and to have no active involvement in any current prosecution or future prosecution until the resolution of the ICAC hearing whereupon the situation will be reviewed.

"It is important to recognise that any individual appearing before ICAC has the presumption of innocence and Ms Cunneen, as with any other NSW citizen, has an absolute entitlement in that regard."

Ms Cunneen has put some of the state's most notorious criminals behind bars, including the Skaf brothers for gang rape.

She was famously prevented from prosecuting a retrial of one of the brothers after talking publicly about the case in a university lecture.

The NSW Bar Association was critical of the decision to remove Ms Cunneen from the case

Ms Cunneen recently presided over the Newcastle inquiry into church sex allegations handing down her findings on May 30, 2014.

A spokeswoman for the NSW DPP has refused to make any further comment on the ICAC matter.

Former Queensland Parliamentary Crime and Misconduct Commissioner Alan MacSporran QC will preside over the three-day ICAC inquiry.

Michael Fordham SC will be Counsel Assisting.