Prime Minister Malcolm Turnbull has defended Employment Minister Michaelia Cash following calls for her to resign over a media tip-off ahead of Australian Federal Police raids on the offices of Bill Shorten’s former union.

Mr Turnbull said the minister had been misled by her senior media adviser’s “wrongful conduct”, after she told a Senate estimates hearing that neither she nor her office had anything to do the tip-off.

Echoing the words of Senator Cash’s cabinet colleagues earlier on Thursday, Mr Turnbull defended Senator Cash and put blame on her aide, David De Garis, who on Wednesday admitted to contacting media and subsequently resigned.

Mr De Garis had “properly resigned” after a “very, very wrong improper act”, he said.

“Once her staffer told her the truth and made the admission that he had done the wrong thing, she corrected the record. She acted entirely properly,” Mr Turnbull told Parliament during Question Time on Thursday.

Labor demanded that Mr Turnbull sack Senator Cash, with Mr Shorten asking the Prime Minister: “How are your ministers meant to be running the country when they can’t even run their office?”

But a defiant Mr Turnbull hit back, attacking Mr Shorten over his union links and dubbing the Opposition Leader “a wholly owned subsidiary of the CFMEU”.

Watch the PM defend Michaelia Cash in Parliament:

Fronting a parliamentary hearing on Wednesday morning, Senator Cash denied five times that media tip-offs regarding AFP raids on the Sydney and Melbourne offices of the Australian Workers’ Union had originated from her office.

But on Wednesday night, her senior media advisor Mr De Garis owned up to leaking the information and resigned.

Senator Cash refused to say whether quitting had been canvassed in a meeting with Mr Turnbull on Thursday morning.

“I will not be going into the ins and outs of the discussions I had with the Prime Minister,” she told the Senate estimates hearing.

Senator Cash also tabled a letter before the estimates committee that she wrote to the Registered Organisations Commission (ROC) after her staffer’s resignation.

“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,” she read aloud.

On Tuesday AFP officers executed warrants sought by the ROC to ensure documents weren’t tampered with or destroyed.

The ROC is investigating $200,000 in donations made by the AWU, including $100,000 given to activist group GetUp! in the 2005/06 financial year while Mr Shorten was the union’s secretary.

The ROC told the estimates hearing on Wednesday night the AWU had refused to hand over all the documents it had requested.

The political headache for the Turnbull government comes a day before the High Court decides the fate of Deputy PM Barnaby Joyce.

Labor MPs taunted Mr Joyce towards the end of question time, with Mr Shorten saying “Catch you later, Barnaby” as the Nationals leader left the chamber.

-with AAP