Treasury has referred to federal police allegations former PwC partner Peter Collins improperly used confidential government information.

As well, a Senate committee is exploring the broader issue of the integrity of consultants, who do billions of dollars of work for the government every year.

The company’s acting chief executive Kristin Stubbins has written to the committee naming four former partners who had been stood aside pending its own investigations.

The email, published by the Australian Financial Review but not yet made public through the committee, named them as  Collins, Michael Bersten, Neil Fuller and Paul McNab.

Stubbins also provided the committee with a list of 63 current and former partners or staff who had received at least one email with confidential information relating to the Multinational Anti-Avoidance Law.

She said these people, who were not named, were likely unaware it was confidential government tax policy information.

The email was written in response to a series of questions from Greens senator Barbara Pocock, who is on the committee which is holding a public hearing on Wednesday.

Treasurer Jim Chalmers said the conduct of PwC in using confidential Treasury advice for commercial gain was a “substantial breach of faith”.

Noting the AFP investigation, Chalmers said the government would consider whether other options would be needed.

“First of all, let’s let the AFP process play out, that’s important. Treasury’s referred it to the AFP and there are other steps we’re working through,” he said on Monday.

“If more needs to be done, we’re prepared to consider it.”

The comments came as Australian Securities and Investments Commission chair Joe Longo told business leaders the regulator was reviewing its contracts with PwC Australia.

Longo said the process of holding the consultancy firm to account was “only just starting”.

“It’s an important part of our economy and they need to be held accountable for this extraordinary incident,” he told the AFR ESG summit.

“It’s a very serious breach of trust.”

The parliamentary inquiry into integrity measures taken by consulting services will hear from the Treasury and finance departments on Wednesday, as well as experts.

The Institute of Management Consultants believes providers should be certified and subject to their constitution and code of conduct to handle government contracts.

“Unlike other professions, the management consulting profession is not regulated in Australia: anyone who wants to call themselves a management consultant can do so,” the peak body said in its submission to the inquiry.

“Requirements for individual consultants engaged on assignments for public sector organisations to hold professional standing would assist in managing risk.”

Chalmers indicated PwC held a “substantial” amount of other government contracts.

“What we have done since being made aware of this really appalling behaviour that people have got a right to be absolutely filthy about, is we’ve worked through a decisive and methodical response on cleaning up the Tax Practitioners Board,” he said.

“The finance department is strengthening their procurement framework and we’re asking people to take into consideration this behaviour when they award future contracts.”

Also listed to give evidence is consultancy firm KPMG Australia.

-with AAP