Two vehicle inspectors in Auckland have been suspended by the NZ Transport Agency for faulty warrant of fitness checks.
The NZTA was also urging more than 5000 drivers who got their warrant of fitness from their inspection centres to get their cars re-checked.
The agency said this afternoon it had suspended Susantha Ranatunga, who worked at Onehunga's Church Street Motors and Tyres.
The suspension was limited to Ranatunga, and the business has retained its warrant of fitness licence.
"Mr Ranatunga was non-compliant in almost every area of his technical inspections," the NZTA said.
"This included brakes, seatbelts, steering, lights and wipers, under body, tyres and exhaust systems.
"We are unaware of specific concerns relating to individual vehicles however, due to the poor quality of Mr Ranatunga's inspections there is a possibility that some vehicles may have been incorrectly passed.
"For this reason we strongly encourage people who have a current Warrant of Fitness issued by Mr Ranatunga to get their vehicle rechecked."
The NZTA said it had also suspended Jet Tyres and Wheel Alignment in the Wairau Valley as an inspecting organisation. The sole inspector at the company, Anderson Lee, was suspended as an inspector.
The Transport Agency said Lee had failed to check some aspects of vehicles during WoF assessments, and that an unauthorised person was carrying out inspections on behalf of Lee.
It said it would contact all affected vehicle owners individually as soon as possible to advise them on recheck options. It would cover the cost of the re-checks.
In all, it was contacting 4053 motorists who had been checked by Ranatunga, and 993 motorists who had been checked by Lee.
Transport Minister Phil Twyford announced last month that law firm Meredith Connell had been brought in by the NZTA board to review 850 open compliance files and had taken over its compliance function because it had failed to carry out its regulatory responsibilities to the standard he expected.
Around 10,000 cars nationwide are expected to need re-checks.