Former Prime Minister Helen Clark says the current system of keeping cannabis illegal is a waste of time and resources.
Clark's foundation has come out strongly in favour of changing the system, saying the current method is failing to dissuade people from using the drug.
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"We're wasting police and justice time chasing anybody for the use of the drug which, on any objective evidence, is causing less harm to society than either tobacco or alcohol," she told The AM Show.
"So let's cut to it, young people have their lives blighted by convictions, it's very arbitrary, there is a lot of police discretion around it, the proportion of young Māori is significantly high.
"I think we ought to focus on getting the laws around it right and then we can focus on the health messaging."
She says alcohol is "immensely worse" than cannabis in terms of damage to people and to society and the public would benefit from regulating the drug, allowing it to be accessed legally at a certain age and certain potency.
"This [cannabis] is a drug that up to 80 percent of Kiwis will use sometime in their lives."
It's the same opinion expressed by the Canadian government, which she met with after it successfully voted to legalise cannabis in 2018.
"The police have to a large extent given up on it so why don't we realise this and say 'let's move to legislate and regulate', that's where the Canadians got to.
"I went to visit the Canadian MP who was in charge of the legislation in Ottowa last year, he had been the police chief in Toronto for years.
"He said to me 'Helen I know what doesn't work, we can't ban it, we can't stop it, we've got to get rules around it'."
Opposition MP and National Party drug spokesperson Paula Bennett strongly disagrees with Clark, though, arguing people aren't being convicted due to drug use.
"In 2018 eight people were in prison for marijuana use and I can tell you there would have been a whole lot more behind that for police to have done that," she told The AM Show.
Overall 1046 people were convicted for cannabis only offences in 2018, 540 of them for cannabis possession and/or use.
Bennett also disputed claims legalisation would lead to an end to the cannabis black market, pointing out a large portion of cannabis users in Canada accessed it illegally.
"You'll be able to buy from the black market, it will be a cheaper product and more potent."
Statistics Canada found in it's National Cannabis survey 42 percent of people using cannabis purchased it from illegal sources. Just over one third, 37 percent, got the drugs from friends and family.
But Clark reckons people given the chance will do the right thing.
"Most people given a choice between doing something legally and illegally will take the legal route, but at the moment we only push everybody down the illegal route."