Community advocate Minnie Ratana told RNZ "it's just blown up, it's like every second person is doing it or has done it''.
When synthetic drugs were banned in 2014, locals starting making it themselves.
Ratana said she knew of children as young as 11 who had started using the drug, and four years later were still "chasing it".
Police believe gangs like Mongrel Mob are linked to the sale of synthetics but locals told RNZ "ordinary people" were making the drug to feed their own addictions, or doing it to make money to survive.