The revelation is among the most sensational developments of the Ombudsman's controversial probe into the bugging affair and comeswhen Mr Kaldas is a contender to become the next NSW police chief commissioner.

Legal sources have confirmed that advice has been sought by Ombudsman Bruce Barbour, who believes there is a prima facie case that Mr Kaldas intentionally misled the ombudsman's office.

The alleged offending occurred when Mr Kaldas was grilled during a lengthy confidential ombudsman's hearing, in which witnesses are required by law to answer all questions honestly.

Mr Kaldas is alleged to have misled the Ombudsman about the source of documents leaked to him in 2012 by former senior NSW crime commission official John Giorgiutti.

If a person is charged and found by a court to have misled the Ombudsman during a confidential hearing, they can face a range of penalties, including a fine or, in extreme cases, a jail sentence.

The documents leaked to Mr Kaldas detailed the improper practices of anti-corruption investigators who conducted extensive monitoring, without due cause, of the phone calls and activities of Mr Kaldas and other police officers between 1999 and 2001.

Any move to charge Mr Kaldas would be extremely controversial as the respected deputy commissioner is a victim of this improper monitoring.

Mr Kaldas is also a whistleblower who helped to expose the improper surveillance.

However, the Ombudsman and the NSW DPP must also weigh up the need to uphold the law that requires all witnesses, including whistleblowers and victims, to give truthful answers during ombudsman hearings.

The DPP can decide not to prosecute if he believes a case is not in the public interest.

As part of an inquiry codenamed Prospect, the Ombudsman is investigating the improper bugging and surveillance of senior police that occurred between 1999 and 2001.

But the Ombudsman is also investigating whether the subsequent leaking of documents about this improper surveillance involved misconduct by police officials.

Some of those involved in the leaking or receiving of these documents have defended their conduct. They claim the files were leaked to police and journalists in 2012 to expose the misconduct that had taken place a decade before.

Mr Barbour recently rebuffed this claim before a NSW parliamentary committee. He told the committee that the leaking may have breached the law and, in some cases, involved highly sensitive documents whose release could not be justified on public interest grounds.

"My task is to apply the law as it has been set down by the parliament … To suggest that my inquiry has focused on targeting whistle blowers is quite simply false," Mr Barbour told the committee.

However, the parliamentary committee's final report included criticism of the Ombudsman's decision to investigate both the bugging scandal and the leaking of documents, saying the dual inquiry had the potential to turn whistleblowers into suspects.

It is likely that the DPP will also examine whether Mr Giorgiutti should be prosecuted for his role in leaking documents, although Mr Giorgiutti also insists he is a whistleblower and should be subject to protection.

A senior NSW police official aware of the push inside the Ombudsman's office to refer Mr Kaldas to the DPP said the move was highly vexed.

The source said that while it appears clear that Mr Kaldas intentionally misled the Ombudsman about Mr Giorgiutti's role in leaking him certain files, there were strong mitigating circumstances that may be used to explain the conduct.

For instance, Mr Kaldas appears to have been trying to protect himself and his source as whistleblowers. But the senior police officer also said the Ombudsman could not allow senior public servants to breach the law about giving truthful answers. All such cases should be referred to the DPP, the source said.

Mr Kaldas has also told a NSW parliamentary inquiry -- which recently concluded he should be given an apology for the manner in which he was monitored in 1999-2001 -- that he was placed under extreme pressure by the Ombudsman's investigators.

Mr Kaldas said while he had expected to be treated as a whistleblower who helped expose the bugging scandal, he instead was faced with "a concerted attack on my integrity and credibility" that felt like "a well-planned attack to silence me as one of the main complainants".

If Mr Kaldas is charged, it will also spark fresh debate about the Ombudsman's use of his extraordinary powers, which include the power to compel a witness to answer questions, and whether there is sufficient oversight of the Ombudsman.

Earlier this year, Mr Kaldas' lawyers wrote to the parliamentary committee conceding that he had given a "partial, incomplete and incorrect account" to the Ombudsman of who had leaked him the files after he was "ambushed" by ombudsman investigators.

"These tactics and this line of inquiry had the effect that Deputy Commissioner Kaldas found it impossible to cope with the examination of the Ombudsman – particularly in the afternoon and early evening."

Mr Kaldas' lawyers also stated that, after further intense questioning, Mr Kaldas later corrected his earlier account and named the source of some of the documents leaked to him.