Andrew Yates fell on his sword on May 29 when a federal joint parliamentary committee raised allegations against KPMG, which holds more than half a billion dollars of government contracts.
"I don't see myself as a bad apple," he told the committee sitting in Canberra on Friday.
"I see someone who took accountability for things that went wrong and nor do I see the firm to be full of bad apples.
"We're a large, complex organisation and we're fallible."
KPMG is feeling the heat over the alleged misuse of confidential board papers and the treatment of a staff member who raised concerns.
In 2023, the employee complained that audit team members had shared information in construction company Lendlease's board papers with others seeking the audit work of corporations such as Westpac.
Mr Yates resigned along with KMPG audit head Julian McPherson.
Committee chair and Labor senator Deborah O'Neill made Mr McPherson read onto the record a 2024 statement from the whistleblower outlining their concerns.
"I have seen a number of actions taken by individuals that are quite clearly not up to the ethical standards of KPMG, or the expectations of regulators, governments, or the public at large," he read.
"It is KPMG's toxic culture and its thirst for improved partner remuneration at all costs that have resulted in them (their concerns) not being listened to or acted upon."
As the hearing continued, the number of people watching the inquiry on the committee's YouTube channel headed toward 6000, from 850 when the hearing began after 8.15am.
Earlier, the chief executive and chair of Lendlease reiterated their disappointment with KPMG and confirmed the company was preparing to find a new auditor after 68 years with the consultancy.
Lendlease will put the contract out for tender once its current audit needs are completed, likely after its first-half accounts in early 2027.
"In terms of trust, it's led to the decisions we've had to make as a company around tendering the audit next year," chief executive Tony Lombardo said.
Chair John Gillam added that it was "a very disappointing set of circumstances", and the board had made certain the current KPMG audit team was being led by someone "completely untainted" by the alleged events.
"What we're dealing with here ... is a few very senior people have had a grave misuse of the access privilege they have, and there's a fundamental breach of trust," he said.
KPMG, one of the top four consultancies in the world, in May set up an independent review into the Lendlease concerns and apologised to the whistleblower.
The scandal has caused a political storm as KPMG handles sensitive public service contracts for the federal and various state governments.
Earlier in the week, the federal finance department placed a three-month moratorium on KPMG bidding for new contracts, while Greens committee member Barbara Pocock referred the firm to the National Anti-Corruption Commission.
The government has 297 active contracts with KPMG valued at $653 million.
