It comes as Prime Minister Anthony Albanese said the firm should name those involved in the scandal.

The government confidentiality scandal first surfaced in January after then-head of international tax, Peter Collins, was revealed to have shared privileged information on the Australian Taxation Office's multinational tax avoidance strategy with others in the firm.

The information was then passed on to clients of PwC.

The incident was referred to the Australian Federal Police for investigation last week by the Treasury Department.

Acting chief executive officer Kristin Stubbins issued an apology to the federal government on Monday, acknowledging the incident had betrayed its trust.

In an open letter published in the Australian Financial Review, Ms Stubbins said nine partners, including members of the firm's executive board and governance board, will go on leave pending the outcome of an internal investigation.

PwC chairperson Tracey Kennair and governance board risk chairman Paddy Carney are among the nine members.

Prominent business leader Dr Ziggy Switkowski was asked to lead an independent review of the firm's governance, accountability and culture in May.

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"Although investigations are still underway, we know enough about what went wrong to acknowledge that this situation was completely unacceptable," Ms Stubbins said in the letter.

"No amount of words can make it right. But I am fully committed to taking all necessary actions to re-earn the trust of our stakeholders.

"And, as we work through this process, I am committed to being fully transparent."

Ms Stubbins said the firm was working to "ringfence" its federal government contracts to prevent conflicts of interests.

The federal government had active contracts with PwC worth $255.2 million as at May 16.

Mr Albanese on Monday morning called the incident "completely unacceptable", suggesting the names of those involved be made public.

"All of this should become public at the appropriate time, of course there are investigations under way and I don't want to say anything to interfere with those processes," he told Sydney radio station 2SM.

Greens senator Barbara Pocock last week sought to release the list of names of employees who had leaked confidential Treasury information during an estimates hearing.

Finance department officials, however, said naming the partners involved in the tax advice scandal could disrupt the criminal investigation.

Ms Stubbins in her letter said the "vast majority" named in redacted PwC emails tabled in the Senate in early May were not involved in any wrongdoing.

"There has been an assumption by some that all those whose names have been redacted must necessarily be involved in wrongdoing. That is incorrect," she said.

"Based on our ongoing investigation, we believe that the vast majority of the recipients of these emails are neither responsible for, nor were knowingly involved in any confidentiality breach."

Finance Department secretary Jenny Wilkinson told senators in an estimates hearing last week PwC had agreed to remove personnel "directly involved in or who had knowledge" of the confidentiality breach from all existing and future contracts under its management advisory services panel until Dr Switkowski's review is completed.

Ms Wilkinson said the firm also agreed to a recommendation that "those personnel not be involved in any other Commonwealth contract".

Senior federal police officers confirmed they had received Treasury's referral but said it was not yet an active investigation.