She said the department later became aware through news reports earlier this month thatmore than 50 staff had knowledge of the confidential tax information.

“This additional information raised serious concerns about the broader culture within PwC and undermined our confidence in their earlier engagements with Finance around this matter,” Wilkinson said.

Labor senator Deborah O’Neil asked how the department could trust PwC to remove all the involved staff,given the firm’s recent interactions with Finance,unless it knew the names of the workers involved.

“How else do you check,verify what they’ve done?” she asked.

Andrew Jaggers,deputy secretary of the Finance Department’s commercial group,said the department has not asked for that at this stage given the impending AFP investigation.

“We’ve indicated that we need assurance and independent assurance around people being stood down off Commonwealth contracts,” he said.

PwC has said it deeply regrets “that we have failed the high standards we set for ourselves as an organisation”.

“We now need to re-earn trust,which is why we have taken appropriate action,including the announcement that we will establish an independent review in relation to our governance,accountability and culture.”

Other firms are concerned about the building scandal. On Thursday,KPMG sent an email to staff saying there had been significant exposure of the “grave issue” in past weeks.

“We can no longer sit by and watch our profession be tarnished by the unethical actions of a few,” the email said.

KPMG told staff that working with government was a privilege,and acknowledged the firm had in the past “got it wrong” but had since learnt from past experiences. It urged workers to re-familiarise themselves with the company’s code of conduct.

Earlier on Thursday AFP deputy commissioner Ian McCartney confirmed police were investigating a person relating to the PwC tax scandal,and said they would look at further people if necessary as the investigation continued.

“It’s now an active investigation,” McCartney said.

McCartney said the AFP was investigating potential breaches of a federal law,which prohibits the release of confidential information by Commonwealth officers. The offences are punishable by up to two years in prison.

The AFP also defended its ability to investigate PwC while retaining millions of dollars worth of contracts with the consulting giant.

AFP Commissioner Reece Kershaw rejected suggestions he had a conflict of interest because he is friends with former NSW police commissioner Mick Fuller,now a senior PwC employee. There is no suggestion that Mr Fuller was involved in or knew about the leaked information.

Greens senator David Shoebridge said it was an “impossible conflict of interest” for the AFP to investigate the firm’s conduct while granting it access to its systems as an internal auditor,and pressed the organisation to sever its relationship with PwC.

The AFP awarded Fuller a contract in his PwC capacity to prepare a report on ACT Policing. According to the parliamentary library,the AFP has six current contracts with PwC worth $6.73 million.

Kershaw said he could understand that it might look like the AFP had a conflict of interest because it was investigating a former senior official at the firm while continuing to work with the company.

But he said he had confidence in the integrity of the AFP’s processes because the organisation was good at “compartmentalising” its work.

With Colin Kruger

Cut through the noise of federal politics with news,views and expert analysis from Jacqueline Maley. Subscribers can sign up to our weekly Inside Politics newsletterhere.