A gunsmith living and working in Canterbury says he told police less than six months ago they needed to look at the rise of white supremacists with guns in Christchurch.
But police said an officer who spoke at public forums last year could not recall a person specifically raising these concerns.
Hamish Bruce helps put together gun show events, battle re-enactments and provides armoury for films.
Mr Bruce said at a meeting in October last year to discuss the Arms Act, he told superintendent Mike McIlraith he was seeing more people with extremist views attending gun events and legally gaining firearms licences.
He said they had started to attend re-enactments he was involved with.
"I did warn him specifically that there were real neo-Nazis out there and they had gained access to all manner of firearms... I'm talking about machine guns, pistols, submachine guns, the whole gamut of what's available to restricted collectors."
Mr Bruce said police needed to know.
"I'd noticed that some of the associates of these groups, I felt, were particularly unsavoury.
"Years ago I was quite politically active in Christchurch, in the late 80s and early 90s, with the skinhead scene - we were anti that - and I knew some of them at that time and I was seeing these faces come back again and so I knew what these people's history had been in the past and it set my alarm bells ringing.
"I thought at least he can get his intelligence people to at least have a squiz at it."
Mr Bruce said they had talked about setting up a meeting to discuss it further.
"He said he would look into it and he did say he wanted to talk about it further but unfortunately we never got the chance."
In a statement police said Mike McIlraith spoke at 12 public forums in six locations around New Zealand in October 2018.
"All the forums were well attended, including Christchurch which had more than 100 people. Questions, observations and commentary were free-flowing and quickly moved back and forth between a range of firearms-related topics.
"Acting Superintendent McIlraith states he cannot recall an individual specifically raising concerns of this nature in the mix of all the forums he presented at.
"Police strongly encourage the person who contacted Radio New Zealand to contact Canterbury Police and provide any information they may have relating to their concerns."