It's unclear how many unsafe vehicles are on the road after it was discovered the New Zealand Transport Agency (NZTA), for the past two years, has not been carrying out proper checks on companies that certify vehicles.
As a result, a review into vehicle certifications is now underway.
Investigations by RNZ reporter Phil Pennington uncovered a series of failings in truck certifications. In August, the NZTA issued an alert requiring urgent checks on the towing connections of almost 500 heavy vehicles, including truck-trailers.
Transport Minister Phil Twyford announced this morning that independent lawyers are conducting a review of 850 open compliance files. About 152 of them require urgent legal or investigative review.
That work is expected to be completed by early November.
"Where certifications need to be revoked or other action taken - that will happen," he said.
"I am disappointed that the agency has failed to carry out its regulatory responsibilities to the standard that I expect, but I am pleased that the board has taken swift action to put this right."
Mr Twyford said years of underfunding was, in part, to blame.
"When problems with these companies were identified there was often no follow-up. This was due to process failures and under-resourcing over the last decade."
"We will look into how this went on for so long, years of underfunding is clearly at the heart of it. This failure, in my view, was in part a result of a reduced focus on the agency's regulatory role over the last decade."
Mr Twyford said it was clear a number of unsafe vehicles have been on the roads.
NZTA chief executive Fergus Gammie said from now on it would be more heavy-headed.
"Quite simply, the approach which the transport agency has traditionally taken has relied too heavily on education and encouragement and not enough on law enforcement."
"Too often enforcement has been seen as a last resort. Let me be clear - that approach is changing."
NZTA board chair Michael Stiassny agreed.
He said it was clear the current system was not working.
"The agency's regulatory compliance system is not working. It's under-performing and it has failed in parts.
"In some cases enforcement has been neither sufficiently robust nor swift enough."
He said NZTA was working hard to fix the system.
"We're doing that now with more resource, more inspectors and a tougher compliance regime."
"Education and reliance on the industry to self-regulate has not worked."
"I can reassure the public that these [problems] are being urgently addressed with the support of the law firm Meredith Connell, who are undertaking a comprehensive review."
NZTA regulates transport sector licence operators and vehicle certifiers.
Mr Twyford said the NZTA board would report back to him regularly during the investigation.