The Australian Workers' Union has lodged a freedom of information request with the office of federal Employment Minister Michaelia Cash to try and determine exactly when she learned about police raids on the union's offices in Sydney and Melbourne.
AWU national secretary Daniel Walton on Thursday said the union had requested any correspondence between Senator Cash, her office and the Registered Organisations Commission, in addition to any correspondence between the minister and relevant staff members.
This could include any text messages, emails and phone lists.
The minister claims she first learned of Tuesday afternoon's Australian Federal Police raids when she saw the news on television.
But Mr Walton argues that story doesn't pass the pub test.
He says a number of journalists have told him they received a tip-off from Senator Cash's office.
It was extraordinary to suggest her staffer didn't pass on the same information to the minister, Mr Walton told reporters in Sydney.
"Michaelia Cash's staffer was made aware of this, they tipped off the media (and) I believe there are most likely documents that prove Michaelia Cash was made aware of this as well."
Senator Cash on Wednesday initially denied her office was responsible for informing the media but later admitted her senior media adviser had tipped off reporters.
The senator on Thursday denied her former adviser "took a bullet" for her by quitting.
Federal Labor is demanding the minister quit or be sacked by Prime Minister Malcolm Turnbull.
