A major privacy breach in the firearms buyback database poses a serious safety risk, National leader Simon Bridges says.
Police said today only one person had access to the data, according to the system's records, and the website was shutdown as soon as they were made aware.
The person was a licenced firearms dealer who reported it to the police this morning, Deputy Commissioner Mike Clement said.
Last week the system was updated, inadvertently giving dealers access to people's personal information. That update wasn't authorised by police, Mr Clement said.
But it's not known how many people's data was breached or how widely circulated it was.
Fair and Reasonable, an anti-buyback lobby group run by the Council of Licenced Firearms Owners (COLFO), claimed the issue was reported by a number of its supporters and that they were able to download and take screenshots of the information.
Mr Bridges told media today it's a "not just a privacy breach, but a serious safety breach".
"What we have today means a complete breach of trust for those [firearms owners] who have come forward."
He put the blame squarely on Prime Minister Jacinda Ardern and Police Minister Stuart Nash, although emphasised he's not calling for Mr Nash to resign "today".
"It's so fresh and we still don't know enough.
"She and her minister Stuart Nash are accountable and responsible for this serious failure."
Mr Clement called the breach an "isolated incident" caused by human error.
Despite the allegations up to 15 people had access, he said information from the vendor shows only one person accessed the data - the person who reported it to the police.
"I would want to believe they did the responsible thing with the information they were able to access."
He said it wasn't the fault of the New Zealand police as the system was built and run by German-based global software platform SAP.
Police are still working with the software provider to find out how many people were impacted by the breach.
The buyback is part of an amnesty period after several types of firearms were banned in the wake of the Christchurch terror attack in March.
Firearms owners are able to hand back their now-illegal guns in exchange for cash.