The federal government has skirted around calls to refer the fast-evolving PwC tax scandal to the new National Anti-Corruption Commission.
The screws have been tightening on the consultancy giant since it came to light that a partner at the firm shared confidential tax information from Treasury to help clients swerve a crackdown on multinationals' tax avoidance.
Attorney-General Mark Dreyfus said it was important PwC was held "fully accountable" for its actions but refused to comment on whether it could be referred to the commission, which becomes operational on July 1.
He said the commission, which becomes operational next month, would choose what it investigated.
While the AFP is investigating Peter-John Collins, the former partner caught leaking the information, the Greens have called for harsher sanctions on the firm and plan to refer the matter to the anti-corruption watchdog.
Greens senator David Shoebridge said the narrow referral of just one PwC partner to the police was inadequate.
"We can't understand why the federal government, having just taken us through this journey of establishing a National Anti Corruption Commission, won't send PwC there," the senator said on Thursday.
He said millions of Australians would agree it was a matter for the new commission.
Malcolm Turnbull, who was Liberal prime minister when the tax information was leaked, was unsure if the "mind-boggling" incident 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.
The former prime minister said the government developed the tax policy in-house and it was "normal business" within Treasury to engage consultants under a confidentiality agreement to offer feedback.
Mr Turnbull said it was "shocking" it had taken so long to come to light and the Australian Taxation Office felt it was unable to reveal the misconduct because of 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 (TPB), which eventually terminated Mr Collins' registration over sharing secret information with other staff.
The incident only became public knowledge when the board published the decision on the Collins matter.
The federal government's close relationship with PwC has also been in the spotlight.
A department with links to Australia's commercially sensitive resources, manufacturing and technology sectors is the latest to reveal it is reviewing dealings with PwC.
Meghan Quinn, head of the Department of Industry, Science and Resources, said its contracts with the consulting firm had confidentiality clauses to ensure information was not used for commercial gain.
"We have taken steps to assure ourselves or to seek assurance from PwC about the protection of our information," Ms Quinn said.
"We are reviewing our engagement with PwC."
Also on Thursday, the Education Department revealed it had nine contracts with PwC worth $8.2 million going back to 2021, including one signed after the TPB announced its action.
