National chairman Martin Sheppard will leave the company shortly, along with audit partners Paul Rogers and Eileen Hoggett.
Mr Rogers and Ms Hoggett had been named in parliament for allegedly accessing confidential information from long-term audit client Lendlease with other KPMG staff to help them win additional contracts.
A whistleblower revealed the purported misconduct while also alleging mishandling of documents from Macquarie Group, Westpac, Dexus and Optus.
Several top KPMG staff including former chief executive Andrew Yates have already resigned over the scandal, which was the subject of a blockbuster hearing on Friday that included scorching criticism of the firm.
"The parliamentary committee's inquiries highlighted issues, including unethical behaviour by senior personnel and the human impact of KPMG's handling of the whistleblower," said KPMG's interim chief executive, Stan Stavros.
"KPMG Australia is focused on ensuring those failings are understood, addressed and not repeated."
Mr Sheppard was hauled over the coals by senators at the committee hearing for his firm's initial refusal to hand over internal documents, citing confidentiality, professional privilege and the risk of prejudicing the administration of justice.
Committee chair Deborah O'Neill described the move as an insult while flagging that KPMG could be investigated for contempt.
The consulting firm later relented and began producing material for the committee.
KPMG on Tuesday said it would overhaul its governance arrangements, including appointing its first independent chair and independent members to its Australian board.
The firm will also review and update the board's role and remit, and appoint new independent board members in priority areas such as audit quality, ethics, whistleblower oversight and other matters of public interest.
An external third party will be appointed to undertake an immediate lessons-learned review into the whistleblower matter.
"The decisions announced today are necessary and immediate," Mr Stavros said in a statement.
"We did not meet the standards expected of us and we recognise the impact this has had on the whistleblower, our people, our clients and the community.
"Trust will only be rebuilt through sustained action and demonstrable change. We are determined to confront what went wrong, act transparently and ensure these failings are not repeated."
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