A report provided to Parliament's commerce select committee has criticised trustees for being slow to pick up financial irregularities in finance companies they were appointed to monitor.
Thirty finance companies failed between 2006 and 2008.
The report, by Registrar of Companies Neville Harris, says the failings were largely due to poor management performance.
He also cites a pattern of director involvement in previous failed ventures.
However, Mr Harris also lays blame at the door of trustees who he says were slow to detect adverse financial issues and did not appear to have enough experienced staff.
Trustee Corporations Association chairman Clynton Hardy says says there have been many instances where directors of organisations such as finance companies have not done their job properly and have not reported to the trustee, as they are obliged to do by law.
"Trustees have been misled and trustees have been kept in the dark," he says. "We've had to go foraging for information, and we've found it."
New Zealand's five corporate trustees are charged with overseeing any non-bank financial institution that wants to raise funds from the public.
Securities Commission chair Jane Diplock says a bolstering of regulation last year has helped increase the powers of trustees.
However she says the arrangement whereby trustees are paid directly by the finance companies still needs review.
ACT MP John Boscawen, who sits on the commerce select committee, wants support for a wider official inquiry in to the finance company scandals.