In an interim report titled PwC: The Cover-up Worsens the Crime, senators criticised the firm for so-called "problematic" engagement with the finance and public administration committee.

The committee has been examining allegations that PwC Australia's former head of international tax, Peter-John Collins, shared confidential information from a Treasury briefing with other staff and partners.

It has also considered the culture and integrity of consulting firms which, collectively, receive billions in government contracts each year.

In another interim report, released in June 2023, the committee accused PwC of committing a "calculated breach of trust", and called on the firm to release further information about those involved.

The latest report, authored by Liberal senator Richard Colbeck, said the committee remained unconvinced by PwC's response to the scandal.

"Beyond superficial commitments to change, the committee has seen nothing of real substance yet," it reads.

"PwC have still made no genuine effort to fully investigate and address the issues.

"Rather their ongoing approach appears to be to hide behind legal professional privilege and hope it will all go away."

The committee did note steps taken by the firm, including commissioning an independent review, adopting the ASX corporate governance principles and establishing a new governance board with an independent chair.

But senators remain critical of the firm's engagement with Parliament, as it has sought to piece together the events which led up to and followed the scandal.

"The committee is disappointed at the lack of substantive answers to questions, a failure to fully disclose important operational matters, and the failure to provide important documents such as the Linklaters report," the report reads.

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The Linklaters report was commissioned by PwC International to investigate whether the confidential information had reached international partners.

Though the review found no international PwC staff had used the confidential information for commercial gain, it did indicate six individuals should have questioned whether the information they received was confidential.

"PwC's continued refusal to provide the Linklaters report is symptomatic of its problematic engagement with the committee," the report states.

Senators questioned how the big four firm could recover their reputation with the Parliament, "while it continues to cover up". "Indeed, the cover-up worsens the crime," the report concludes.