Attorney-General Mark Dreyfus says consultancy firm PwC must be “fully accountable” for the tax scandal, but would not be drawn on referring it to the new anti-corruption commission.

Mr Dreyfus said the allegations were “deeply troubling” and would be investigated by the Australian Federal Police.

The screws have been tightening on PwC since it came to light that a staff member shared confidential tax information from Treasury to help clients swerve a crackdown on multinationals’ tax avoidance.

“What’s important is that PwC be fully accountable for their actions,” Mr Dreyfus told ABC Radio.

“I’m not going to make a comment on whether or not any matter could be referred to the National Anti-Corruption Commission.”

He said the commission would choose what it investigated.

The Greens plan to refer PwC to the anti-corruption watchdog when it becomes operational next month.

Malcolm Turnbull, who was prime minister when the tax information was leaked, was unsure if the incident, while “mind-boggling”, fell under the remit of the anti-corruption commission.

“But certainly it should be pursued in the greatest diligence,” he told ABC Radio.

Mr Turnbull said he knew nothing about the confidentiality breach and would be “very surprised” if the then treasurer, Scott Morrison, was aware of the details.

“My government, particularly myself and Scott Morrison, the treasurer, were determined to crack down on multinationals avoiding Australian tax,” he said.

Mr Turnbull said the government developed the tax policy in-house and it was “normal business” within Treasury to then engage consultants under a confidentiality agreement to offer feedback.

He also said it was “shocking” that it took so long to come to light and that the Australian Taxation Office felt it was unable to reveal the misconduct because of its own strict secrecy rules.

The ATO first became aware of the potential breach of confidentiality in 2017.

The matter was referred to federal police in 2018, but the agencies decided there was not enough evidence to launch a criminal investigation.

The ATO then took it to the Tax Practitioners Board, which eventually scrapped the registration of former partner Peter-John Collins over sharing secret information with other staff.

The incident only became public knowledge when the board published the decision on the Collins matter.

PwC has also been under pressure to reveal the names of those involved in the leak.

Asked if the names of the nine partners PwC stood down should be made public, Mr Dreyfus said the matter had “some way to run yet”.

“The matter of the names is part of the continuing investigation, the continuing handling in this matter by the Tax Practitioners Board and no doubt in the investigation by the Australian Federal Police,” he said.

The federal government’s close relationship with PwC has also been in the spotlight, with the Greens urging the Commonwealth to ban contracts with the company.

On Thursday, a parliamentary committee was told the Education Department had nine contracts with PwC worth $8.2 million going back to 2021, including one signed after the TPB announced its action.

Secretary Tony Cook said the department was “obviously gravely concerned” about the behaviour of PwC and had written to the company.

“What they have done is totally unacceptable,” he said.

“We are working with Treasury and Finance … and seeking from (PwC) further information about officers involved in those contracts.”

– AAP