NZTA is warning 10,000 drivers their warrant of fitness may be dodgy.
That's almost double the number already revealed, after warnings went out to 5500 vehicles from two suspended garages.
The new warnings include almost 3500 customers who got their warrants from Orient Motors in Glenfield, Auckland and 600 who got warrants from Te Aroha Automotive who need to get them rechecked.
The agency "is stepping up enforcement action for non-compliance across all regulatory areas for which it has responsibility", said Meredith Connell's Steve Haszard who took over managing road safety compliance last month after the New Zealand Transport Agency admitted failing to enforce the rules for years, and the government ordered a review into it.
Drivers can have their vehicles re-checked free of charge with a NZTA voucher.
The Transport Agency says action is being taken against 74 vehicle testing businesses or inspectors, and vehicle operators, including 13 immediate suspensions.
This follows the law firm Meredith Connell today completing its review of 150 of the most urgent, open files at the Transport Agency. Another 700 files are still being checked.
The public would notice further enforcement actions over the coming weeks, said NZTA.
Some of the names of those facing action have been withheld as legal action is underway.
One unnamed provider of driver licensing courses has had its right to do the work revoked. It's the only immediate revocation amid an unprecedented wave of action by the agency.
"In some instances the risk to land transport safety or public safety is such that a company or individual is immediately suspended" without having to go through warning steps, the agency said in a statement.
Four transport services have also been immediately suspended, all of them unnamed heavy vehicle drivers.
"There is a very narrow ability to suspend a transport service licence holder. It can only occur if the transport service does not hold a certificate of knowledge, law and practice," the agency said.
Another 45 transport services and two service providers have been hit with a proposal to revoke their right to operate.
Nine warnings have also gone out - eight to transport services, which raised problems that now must be addressed.
The review of the 150 most urgent cases had revealed some "really concerning" behaviour by companies and individuals like the four truckies who have been suspended, said Mr Haszard .
Twenty truck companies are now on revocation notices of their licences and could be closed down. As the 20 companies had multiple trucks on the road, this was the priority, he said.
"So that's why we're moving as quickly as we can to get through the revocation process - some of those [truck company revocations] are coming in quite soon, like over the next week or two weeks."
Others, however, would not be sorted out before Christmas, he said.
"If there's a significant safety issue they won't be on the road but until such time that's determined and the process is followed that we have to follow, that's the position."
For three of the four suspended truck drivers "it was their traffic history, their convictions, which we said was ill-suited to them remaining in the industry and continuing to drive".
"And for one of the drivers it was a medical condition which we felt meant he should no longer be driving."
The Transport Agency had not taken compliance action over these driver and company failings before now, he said. But the nationwide investigation underway now had made "significant progress".
Of another 700 files facing Meredith Connell, it has looked at nearly a third of those and should have finished that in the next six to eight weeks.
It remained unclear what proportion of the almost 10,000 warrants of fitness subject to rechecks might actually be faulty, Mr Haszard said. But they had found that garages were failing to check brakes, seatbelts and steering systems.
Up to 2000 trucks had already had their certifications revoked, before Meredith Connell was even called in by the Transport Agency's board as an emergency measure in October.