Home Affairs secretary Michael Pezzullo has said the public servant who leaked a top secret document he authored should be sent to jail, and he was "heartened" to hear police were closing in on a suspect.
Australian Federal Police assistant commissioner Neil Gaughan told a parliamentary hearing "there is significant concern" around the alleged leaker of a document that led to a raid on the home of a journalist in June.
"There is significant concern around where that person potentially sits within the bureaucracy," Mr Gaughan said.
Despite initially saying he had forgotten about the investigation into the leak of the document, Mr Pezzullo let fly on Tuesday morning, saying the document had been leaked as part of a "Canberra game".
"The person who gave [journalist Annika Smethurst] the document broke two confidences. One is they leaked a top secret document and frankly, subject to judicial process and fair process, they should go to jail for that.
"And secondly it was designed to play into a Canberra game about which agency is asking other agencies to expand its powers or remit and its completely unacceptable for public servants to be playing in that way."
Mr Pezzullo said news the police were closing in on a suspect filled him with optimism the law would be applied.
"I'd resiled myself to the fact that they weren't going to find the leaker, and now I'm heartened by the fact they might."
In earlier evidence the Australian Federal Police had said the investigation into the leak was open, and refused to rule out whether journalist Annika Smethurst was also the subject of an investigation.
"It remains the case that the investigation is ongoing, so I'm not drawing anyone in or out of who may be have been determined or who we may determine has committed a crime," Commissioner Andrew Colvin said.
In June Ms Smethurst's home was raided, 14 months after she published a story suggesting the Australian Signals Directorate could spy on Australians. The article included a screenshot of a document marked Top Secret and AUSTEO (Australian Eyes Only).
Mr Pezzullo said he knew the document "intimately" because he had written it to Defence Secretary Greg Moriarty, and the reporting was incorrect.
It is completely unacceptable for someone to have given the journalist this document, or passed on a screenshot or some sort of imagery of it.Mike Pezzullo
"It was a whistle blown on a falsehood."
The leaking of the document led to "direct discussions" about trust between himself, Mr Moriarty and Australian Signals Directorate director-general Mike Burgess, Mr Pezzullo said. It also had the ability to break down trust between the government and the public service.
"That has a cascading effect all through the service because it becomes clear that there is someone who has, frankly, done the wrong thing."
In an impassioned speech, Mr Pezzullo held up a copy of the newspaper article from last year, criticising both the reporting and the leaking of the document.
"It is completely unacceptable for someone to have given the journalist this document, or passed on a screenshot or some sort of imagery of it.
"It is a crime and, as Mr Gaughan said, the concerns they have and the reasons why that investigation is ongoing is they are particularly concerned about the likely location of that person within the bureaucracy."