Investigators are looking urgently at whether to re-inspect vehicles signed off as if they were repaired by an Auckland certifier who's been suspended.
The Transport Agency says repair certifier Dale Barlass has admitted certifying a vehicle even though it was still damaged.
Complaints were lodged against Mr Barlass, of Impact Certifiers, who admitted to failing to follow vehicle standard requirements when inspecting and certifying, the agency said.
He also admitted not using manufacturers' repair processes.
"A formal investigation will urgently look at whether we need to revoke any of the certifications Mr Barlass has issued and whether we'll need to re-inspect any vehicles," NZTA's chief executive Fergus Gammie said in a statement.
"This work will be completed as quickly as possible, in order to give vehicle owners certainty."
Mr Barlass is the third vehicle inspector to be suspended, as lawyers investigate 152 cases where there are safety worries. Another 650 less urgent cases also remain to be looked into.
The other two suspended inspectors were part of a separate legal process that needed to run its course before the agency could name them, it said.
Mr Barlass has been approached for comment.
The inspector suspensions come on top of the suspensions of four heavy vehicle certifying engineers over safety concerns.
Law firm Meredith Connell was called in last month to investigate after the Transport Agency admitted failing to enforce road safety regulations for years.
"We have acknowledged that our previous approach has been neither sufficiently robust nor swift enough to ensure the highest levels of regulatory compliance in the past. Now we are putting it right," Mr Gammie said.
"New Zealanders can expect full accountability and an increased number of enforcement actions."
Repair certifiers are approved by the agency to inspect badly damaged or deteriorated vehicles, for instance after a crash.
The law requires that repairs restore the vehicle to a similar condition to when they were manufactured, whether these are structural, mechanical or electrical repairs.