Former employment minister has given no extra details to police, after invoking public interest immunity during Senate hearings

Michaelia Cash did not provide any additional information to police investigating the tipoff to the media about the raid on the Australian Workers’ Union headquarters, leading Labor to accuse her of refusing to cooperate with the police.

Guardian Australia understands the former employment minister’s evidence to the police consisted of only a witness statement detailing her evidence already in the public domain and she was not asked follow-up questions.

Michaelia Cash aide resigns over AWU raid tip-off to media Read more

While Labor leapt on the revelation as a sign of Cash’s evasiveness on the AWU raid leak, sources close to Cash believe it supports her version of events that neither she nor her office is under investigation.

The Australian Financial Review, which first reported the revelation, suggested the leak made Cash a victim of payback culture within the Liberal party after she helped depose Malcolm Turnbull in last week’s leadership clash.

A senior Liberal source was quoted as saying that Cash was “asked to cooperate and she didn’t”, although Cash insists she did cooperate with the police but simply did not know anything more about the tipoff.

In October, journalists and television cameras were present when the police raided the AWU headquarters as part of the Registered Organisations Commission’s investigation into $100,000 in donations from the union to the campaign group GetUp in 2005.

Play Video 1:35 I am 'absolutely not covering up' AWU raid, says Michaelia Cash – video

In Senate estimates, Cash repeatedly denied that her office was involved, but on 25 October her then senior media adviser David De Garis resigned after Buzzfeed revealed that he had tipped off the media about the raid.

Cash corrected her evidence, claiming the tipoff was made without her knowledge after her staff member found out about the raid “from a media source”. The AFP then set up an investigation into the leak.

Since then, Cash has repeatedly invoked public interest immunity in refusing to answer further questions about the tipoff.

On Friday, the acting shadow employment minister Tanya Plibersek said the revelation was “yet another example of the minister going out of her way to avoid scrutiny”.

“It is absolutely unacceptable that Senator Cash continues to be a minister yet reportedly refuses to cooperate with an AFP investigation,” she said.

The Labor senator Kimberley Kitching suggested Cash’s responses on the leak inquiry were circular because she “tells the Senate she can’t answer questions ... because there’s a police probe” and “tells [the federal police] she won’t answer questions because she’s got nothing to add to what she’s told the Senate”.

Kimberley Kitching 🇦🇺 (@kimbakit) 😡@SenatorCash tells the Senate she can't answer questions about her office's criminal conduct because there's a Police probe



🚔Cash tells @AusFedPolice she won't answer questions because she's got nothing to add to what she's told the Senate #auspolhttps://t.co/AJ01QKyHpe pic.twitter.com/vLNrN7KsXK

A spokeswoman for Cash said: “The minister absolutely refutes the allegations that have been made, as she has refuted them in the past.

“As the minister has consistently said, neither her or her office are under investigation.”

The spokeswoman said the minister “will not be giving a running commentary on misinformation being peddled by the AWU”.

Michaelia Cash claims 'public interest immunity' over union raid tipoff Read more

The Australian federal police has referred material to commonwealth prosecutors relating to the media tipoff, culminating in a full brief of evidence. Police believe at least one offence may have been committed.

The AWU challenges the legality of the raid and is still locked in litigation against the Registered Organisations Commission.

Cash has been issued a subpoena to give evidence in the case, but insists she will apply to have the subpoena set aside.

Cash was moved from her role as employment minister to the jobs and innovation portfolio in December. After the leadership spill that deposed Turnbull, the new prime minister, Scott Morrison, demoted her to minister for small and family business, skills and vocational education.