Senator Michaelia Cash’s former media advisor has admitted he and a staff member of federal minister Michael Keenan tipped off news outlets about raids on a union’s offices to hurt Opposition Leader Bill Shorten.

David de Garis told the Federal Court he and then-justice minister Mr Keenan’s media advisor Michael Tetlow told journalists the federal police were about to raid the Australian Workers Union in October 2017.

The raids were part of investigations into the legality of $100,000 donations the AWU made to left-wing lobby group GetUp in 2006 when the union was led by Mr Shorten who also sat on the lobby group’s board.

“I spoke to a media advisor in the office of the justice minister,” Mr de Garis told the court on Wednesday.

“I understood the raids were going to occur in the offices of the AWU in Melbourne and Sydney and we organised to disseminate the information to the media together.”

The pair decided “amongst themselves” about who they would contact in the media.

“I called several print journalists, Mr Tetlow was calling the TV media,” Mr de Garis told the court.

The former staffer said he did not recall if he told Senator Cash about his decision to contact the media.

“I’d probably remember. I imagine it’s ‘no’,” he said.

Earlier on Wednesday, Mr de Garis admitted the media attention was at least in-part designed to make Mr Shorten look bad.

“It would have at least been part of my thinking, I’m sure,” he said when asked if the impact on Mr Shorten was part of his consideration.

Camera crews showed up at the Melbourne and Sydney offices before Australian Federal Police in a move that raised questions about the motivation behind the raids.

In parliament on Wednesday, Mr Keenan stood by previous comments that no one in his office informed media outlets ahead of the raids.

“I was justice minister for four and a half years. Every single day, myself and my office dealt with sensitive information,” he said.

“We had protocols associated with dealing with that information and we continue to make sure those protocols were adhered to in all circumstances.”

The AWU is arguing, in its case against the Registered Organisations Commission and AFP, that the raids were unlawful.

It’s alleged they were politically motivated and instigated by Senator Cash in a bid to hurt the union and Mr Shorten.

Mr de Garis has previously told the trial he was given information about the impending raids by the senator’s then-chief of staff, Ben Davies.

Mr Davies, Senator Cash and commission executive director Chris Enright are due to give evidence later in the trial.

-AAP