The Australian Federal Police (AFP) has launched an investigation into how the media learned of AFP raids of the Australian Workers' Union offices this week, following BuzzFeed News' story revealing the office of employment minister Michaelia Cash tipped off media about the raids.
Attorney-general George Brandis informed Senate Estimates on Friday morning about the investigation, as the government were due to face a third day of questions.
"Senator Cash's office was advised last night by the Australian Federal Police that they commenced an investigation into that matter," Brandis said.
"In relation to today's proceedings, as the matter is under investigation it would not be appropriate to discuss the matter further. Therefore neither I nor any officer who may be called before the committee this morning will be accepting any questions in relation to that matter at the request of the Australian Federal Police."
Here are the letters which George Brandis have just tabled
Now the matter is being investigated, Brandis says the government cannot answer further questions about the leak.
Brandis read verbatim from a letter sent to Cash's office by the AFP: "As this matter is under investigation it would not be appropriate to discuss the matter further."
Cash's senior media adviser David De Garis resigned from Cash's office on Wednesday night after the story was published, admitting to her that he was behind the leak.
Cash told a Senate Estimates committee on Wednesday night that De Garis told the minister he received the information about the raid from a "media source" but wouldn't disclose who it was. He then passed that information onto other media outlets so they could capture the AFP raiding the union office.
Justice minister Michael Keenan told AAP his office was briefed by the AFP before the warrants were executed, but he was personally not informed until afterwards.
Cash maintains De Garis' actions took place without her knowledge and she did not authorise the leak. She also claims she did not mislead the Senate, despite having to correct the record after denying the leaks five times, because she gave information she understood to be true.
On Thursday morning, Cash tabled a letter she sent to ROC commissioner Mark Bielecki – the organisation who issued the warrant on the AWU executed by the AFP – asking for a full inquiry into the leak.
"I do not have the power to direct you in relation to such a matter, however one course of action which I would ask you to consider is referring the matter to the Australian Federal Police," Cash said in the letter.
Cash said she was not informed about the raids until they had begun in the afternoon – despite the warrants being issued at 9.40am.
"I found out as it unfolded on the television after I returned from a meeting yesterday about 4.45pm on the ABC," Cash said on Wednesday morning.
The minister told Senate Estimates that De Garis was present when she gave prime minister Malcolm Turnbull a briefing about the leaks before Question Time at 2pm.
In Question Time on Tuesday, the prime minister said that Cash had "assured me that she did not advise any journalists about the raid".
Cash refused to detail her conversations with Turnbull, and said she had not considered resigning.
Cash said on Thursday that she had not spoken to De Garis after Estimates finished at 11pm, and attempted to call him at midnight and again this morning but had been unable to reach him. Cash said she was checking his well being, and requesting he come into parliament for a full debrief in her office this afternoon.
De Garis was ordered to secure his computer and laptop as part of the investigation, Cash said.
The minister also said that she had sought assurances from her staff, including her other media advisor, that they were unaware of the raid before it took place.
Bielecki said on Wednesday night he doesn't think any of his staff should be questioned over the leak.
Cash was due to face a third day of questions today, but refused to attend, telling senators she had a prior commitment in Perth.