It was revealed in January that PwC Australia's former head of international tax, Peter Collins, had allegedly shared privileged information on the Australian Taxation Office's multinational tax avoidance strategy to staff at the firm.

In a statement, Treasury said emails tabled by the Tax Practitioners Board tabled in Parliament in early May had "highlighted the significant extent of the unauthorised disclosure of confidential Commonwealth information and the wide range of individuals within PwC who were directly and indirectly privy to the confidential information".

"In light of these recent revelations and the seriousness of this misconduct, the Treasury has referred the matter to the Australian Federal Police to consider commencement of a criminal investigation," it said.

Mr Collins has since been deregistered by the Tax Practitioners Board and banned from the profession for two years.

A Senate committee is currently inquiring into the management and assurance of integrity by consulting services, following the scandal.

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Greens senator Barbara Pocock, a member of the committee responsible for the probe, welcomed the referral, but called on the Albanese government to go a step further and ban contracts with the firm.

"Now we need to know when Labor will commit to a ban on PwC contracts, support for a full investigation by the [National Anti-Corruption Commission] and an end to political donations from big consultants," Senator Pocock said in a statement.

"The bigger question remains, are we looking at just the tip of the iceberg; What is going on in the larger industry of big consulting?"

Senators have grilled departmental officials over their engagements of the firm, and other contracts, during Senate estimates this week.

Responding to questions from Senator Pocock on Monday, PM&C deputy secretary David Williamson confirmed the department was yet to ban the consultancy but said "one of the criteria for value for money in contracts relates to ethical behaviour and certainly we would bring that to bear in contemplation of engaging PwC, or indeed any other consultant".

Treasurer Jim Chalmers on Monday promised to crack down on external consultants who abuse their access to privileged information.

"We've taken some steps [and] there will be more steps to take. I'm working on them, almost literally right now. And I'll have more to say about it in due course," the Treasurer told ABC.