A Massey University researcher says cannabis was "for all intents and purposes" decriminalised in 2010 in New Zealand, and notes the number of arrests has dropped dramatically in recent years.
Associate Professor Chris Wilkins, speaking this morning to TVNZ 1's Breakfast programme, said the number of arrests for cannabis has fallen by about 70 per cent since 1990, as police are increasingly uninterested in punishing people for related offences.
"After 2010, pre-charge warnings meant about half of people now get a warning rather than being prosecuted," Mr Wilkins said.
"For all intents and purposes, we decriminalised cannabis in 2010 - it's just no one's noticed."
Mr Wilkins said police have slowly turned their focus towards fighting methamphetamine - the supply of which has been steadily increasing, including a big surge in 2014.
"It's basically putting your resources into the thing that is causing the most harm and that is methamphetamine," Mr Wilkins said.
"Levels of availability are at their all time high at the moment and prices are declining."
A report from Mr Wilkins' team at Massey this year in May found that methamphetamine is becoming cheaper and easier to find in New Zealand.
An online survey earlier this year also found the number of drug users who said meth was easily accessible increased from 19 per cent in 2015 to 44 per cent in 2016.