Lawyers for Michaelia Cash will again fight a demand for her to front court over the Australian Workers Union raids case, with the Jobs Minister declaring she won’t be “bullied”.

Senator Cash gave a rare media appearance on Wednesday, arguing the reissued subpoena was a “tactic” employed by the AWU, which is engaged in a court battle with the Registered Organisations Committee (ROC).

The development, labelled a revelation by Labor on Wednesday, added to the fallout over the admission her former staffer David De Garis tipped off the media about a federal police raid on the union’s offices.

At a fiery press conference in Parliament on Wednesday, Senator Cash said the subpoena was the third issued at the “AWU’s request”.

“It does not surprise me that the AWU is trying this tactic again,” she said.

“Can I confirm, for the record, because there does seem to be some confusion, I am not a party to these proceedings.”

Senator Cash said she would “comply with the legal process” but had ordered her lawyers to have the “subpoena set aside”. 

Asked on what basis it should be set aside, Senator Cash said: “I do not intend to play the court process out publicly”.

The court set aside a previous request from the AWU in March.

Senator Cash said she would not “be bullied by the Australian Labor Party”, and denied she was engaged in a cover up.

I am standing here at this point in time, how many journalists are here? 15, 20 of you? I am on national television as we speak. I am absolutely making myself available.”

Last year, federal police raided the AWU’s offices as part of a ROC investigation into donations received from the union to the progressive activist group GetUp.

The subpoena reissued on Wednesday requests that Senator Cash, Mr De Garis, former Fair Work Ombudsman media adviser Mark Lee, and ROC official Chris Enright give evidence in August.

They would also have to provide documents requested by the court by June 28.

Senator Cash has said she had no knowledge of the tip-off until Mr De Garis told her what he had done, after the event.

Since the scandal broke, she has refused to answer questions about the issue, citing an ongoing Australian Federal Police investigation into the leak and claiming public interest immunity.

Again on Wednesday, Senator Cash would not answer whether she had been interviewed by the federal police but said she was not under investigation.

Earlier on Wednesday, Labor’s employment spokesman Brendan O’Connor argued Senator Cash’s position was untenable.

He demanded the Prime Minister indicate whether he still backed Senator Cash.

The opposition has been calling for Senator Cash to resign from the ministry since last year.

“There is not a whiteboard big enough for Senator Michaelia Cash to hide behind,” Mr O’Connor said, referring to an incident in Parliament earlier this year when overzealous security staff shielded her from media using a whiteboard

Asked about that incident on Wednesday, Senator Cash said she had “nothing to do with the whiteboard”.

“You should have seen the look on my face. I was the one who surprised,” she said. 

The embattled minister did not appear in Senate Estimates hearings on Wednesday when the ROC was called for a routine appearance.

Instead, junior frontbencher Zed Sesejla represented the government.

The government argues that since Craig Laundy is now the minister responsible for industrial relations, Senator Cash is not required to front these hearings.

Following news of the subpoena, the Employment and Education Committee requested that the minister front the committee on Wednesday.

Malcolm Turnbull has so far backed Senator Cash, though she lost control over industrial relations in a ministerial reshuffle late last year.

In a statement on Wednesday, AWU National Secretary Daniel Walton said the union had “believed last year’s raid – and the investigation itself – to be unlawful”.

“We think it’s vital for the Court is assisted by the evidence of witnesses who we believe are relevant to the issues in the case. That is why we sought subpoenas,” he said.