The former boss of the Registered Master Builders Association is being investigated by officials for potential breaches of the Companies Act.
Blair Cranston was a Master Builders' life member and its president from 2010 to 2012. He was expelled from the organisation in December 2016 for breaches of its code of conduct.
His firm, Cranston Homes, failed last year and liquidator Boris van Delden released his final report to the Companies Office last week.
That report confirmed that tradespeople and others owed $3.6 million by the firm will get nothing back.
Cranston, now working as a real estate agent, told the Herald that out of the $3.6m, interests associated with him were owed between $1.2m and $1.6m.
"I obviously feel regret about the failure of my company. It has cost me everything. I apologise to creditors and customers who have suffered loss. Many have been supportive and understanding, something for which I am grateful," he said.
Cranston was declared bankrupt in March this year. He said he'd reached repayment terms with many of his creditors but one - a debt-buying company - refused to agree to them.
Van Delden's report also says the liquidators passed on information to the Registrar of Companies, which had investigated Cranston's management of the firm.
Asked for comment on that probe, a Companies Office spokeswoman said:
"The Integrity and Enforcement Team of the Companies Office have received information from the liquidator of Cranston Homes (Auckland) Limited to investigate possible breaches of the Companies Act," she said.
"At this point we are unable to disclose any information about our investigation as it is ongoing," she said.
Cranston told the Herald he had not heard from the Companies Office directly about the investigation but had provided answers to questions via the liquidators.