Police and the Government are claiming a successful firearms buy-back despite having no up-to-date estimate of how many guns they expected to be handed in.
Figures supplied by Police Minister Poto Williams are from March 2020 and were never updated to reflect changes to the rules.
The National Party said it shows the buy-back was simply a PR exercise, rather than an effective way to get dangerous guns off the streets.
Williams said: "Police estimated that there would be between 50 and 100 short semi-automatic rifles handed in, between 750 and 1000 firearms containing centrefire lower receivers, and between 1385 and 1700 pump-action centrefire rifles".
Those numbers, from April 1, add up to 2185 and 2800 guns.
According to police, that estimate came from March 2020 and was never updated when the regulations were set for the second buy-back and amnesty.
Inspector Richard Wilson said certain things were taken into account in the estimates that later weren't part of the buy-back.
"For example; it was anticipated originally that collectors would hand in their firearms for compensation," Wilson said.
"However, through regulations it was deemed that semi-automatic pistols held by a collector, museum director/curator, approved employee/member of a broadcaster/theatrical society etc, or as an heirloom/memento, would not be prohibited firearms (so not eligible for compensation) and would be able to be retained by a person with an endorsement on their licence and a permit to possess/import, allowing them to possess that semi-automatic pistol in those noted capacities."
Wilson said police also wanted to provide a generous estimate.
"After the regulations were passed and understood, police were able to directly engage with members of the firearms community.
"Talking to licence holders about what firearms they held also changed our expectations. That is why police are confident this has been a successful buy-back in removing newly prohibited, high-risk firearms from our communities."
She was not able to recall those estimates her office had when asked on Tuesday morning.
Wilson said the buy-back has been successful, despite not having any estimates for how many guns should have been handed in.
"I'm given lots of information from police about guns that are out there but I think you're kind of missing the point here," Williams said.
"The point is, actually, we need to get a better handle on what is in the community and our gun register will go some way to doing that."
Brown said Williams cannot fall back on the need for a gun register when police had been capable of putting together estimates.
"The reality is, the police had an estimate back in March 2020, but more recently after making changes to regulations they didn't have an estimate," Brown said.
"So clearly they've got some information and should have put together a more up to date estimation so they would be able to measure the effectiveness of their buy-back."
"The fact that they didn't have an up-to-date estimate around how many firearms they were hoping to get off the street shows it was just a PR exercise rather than an effective tool to get guns off the streets."
An amnesty now runs until August for people wishing to hand in banned guns, but they will not get compensation.