The Civil Aviation Authority is accused of misleading the public about the number of helicopter inspectors on its staff when a fatal crash killed seven people in 2015.
It originally said there were two, who were stretched by big workloads.
But now it transpires there were at least six people who could do the job.
A Transport Accident Investigation Commission report into the crash criticised the Civil Aviation Authority (CAA) for its lax inspections of the helicopter operator, saying it overlooked failures and did not enforce the rules ahead of the crash.
In May, just days before the official crash report came out, the CAA held a briefing for the media detailing its own failures in the lead-up to the fatal crash.
Deputy Director of General Aviation Steve Moore said there were only two inspectors available to conduct oversight of the country's 100 or so helicopter operations, and that the CAA was struggling to get more staff.
"They could have big workloads," Mr Moore said.
"That might have been a factor in the scrutiny that they were providing of the operators."
Next to Mr Moore throughout the briefing was the board chair, Nigel Gould, who said he had total confidence in the team at the CAA.
A victim's family says in a private meeting with top CAA officials including the Director Graeme Harris and the Chief Legal Counsel on the same day as the briefing, they too were told there were only two inspectors.
But official information shows there were four flight operations inspectors at the time of the crash.
The manager and team leader were also qualified to do the job - taking the total number of inspectors to six.
Now, the CAA says Steve Moore's under-stating of inspector numbers was a mistake.
"Steve said at the time he commented that he thought that this was correct - based on memory not research - he absolutely agrees that after checking it was indeed 4," a CAA spokesperson said via email.
"[Steve] also says that there were only 2 at the time of recertification in 2012 which is where he got the number 2 from."
The CAA declined all interview requests on the matter, and would not say why other top officials gave the same erroneous information to the family.
Transport Minister Phil Twyford also declined to comment on the error, but a spokesperson said he had asked the Ministry of Transport to look into concerns around the CAA's culture and performance regulating helicopters and small aircraft.
A former senior CAA safety staffer who did not want to be named for fear of reprisal, said from memory or not, Mr Moore should have checked the facts before briefing media.
"It was sort of, 'oh woe is us we only had two inspectors and we didn't know what we were doing, and we're really sorry and it won't happen again cos we've now got eight inspectors'," he said.
It seemed Mr Moore was just making up excuses, he said.
The chief executive of industry lobby group Aviation New Zealand John Nicholson said he was confused about why the CAA gave the wrong numbers.
"The fact that the number seems to be changing quite a bit gives you real concern, because if that number's not right - what else is not right," Mr Nicholson said.
It undermined CAA's own arguments about its inspectors' big workloads, he said.
"They've also talked about being under-resourced, over-worked, but if you look at the numbers you'd say well how come," Mr Nicholson said.
One of the Fox Glacier crash victim's families said the CAA had much to answer for.
They said they did not believe much of what they've been told by the CAA, and they no longer trusted it.
Charles Gibson - father of Josephine, who was on the flight - said the mis-stating of inspector numbers showed there were still serious problems at CAA.
"I wasn't confident of getting true answers all the time from them, I believe they were only concerned with making sure their reputation was not tarnished throughout this whole process," he said.
John Nicholson said it was clear the CAA needed to improve so that it could regain the trust of all operators and fulfil its role in keeping us all safe in the skies.
Read the full OIA here: