The NZ Transport Agency has begun contacting about 10,000 Kiwis, whose cars may not have been properly checked during their regular Warrant of Fitness inspection.

Law firm Meredith Connell is reviewing the cases involving cars that may not have been checked properly.

Motor Trade Association chief executive Craig Pomare told Kate Hawkesby it is likely the number of cars needed to be checked will rise. 

"We believe there may be more to come. The 10,000 comes from a review of the most urgent files, and the inspectors we are most concerned about, so as they [the inspectors] head into the other 800 files, we don't think the numbers will be as great but even one is a worry 10,000 is a big worry."

He said with only 18 auditors the NZTA simply doesn't have enough resources to check everyone.

"Each year we do about 6 million inspections and we have got 12,000 inspectors but unfortunately, there are only 18 auditors at the NZTA so they've got a massive workload."

"They work their backsides off but they just haven't got the time and the resource to get around those inspectors, so unfortunately what ends up happening is they end up focusing on the bad boys and the rest get left alone."

"The NZTA is about to appoint another 17 auditors, which is fantastic, and we are hopeful with doubling of resource they are able to get back to their job of keeping an eye on the inspectors."

Pomare said it is really important for the owners of the 10,000 vehicles affected to get their cars checked.

"This is a safety check, it looks at key safety features on your car, your breaks, your tyres, your suspension and a whole lot of other things."

"We want to make sure New Zealanders are safe on the road and the only way to do that is, of course, for us to have confidence in the system."

"Ninety-nine per cent of our inspectors are  fantastic but all you need is one ratbag in there who then tar the rest of the inspectors."