Cannabis referendum: Colorado, Canada aren't good examples for legalisation - expert

New Zealand should look at Uruguay as a good example for how to handle cannabis legalisation, drug researcher Chris Wilkins says.

Dr Wilkins told The AM Show Uruguay has taken a not for profit approach to cannabis, which has allowed for a much lower impact introduction of the drug.

"People can access cannabis in three ways: grow their own, social club or from a pharmacy... It's going fairly well.

"What they're finding is that grow your own is the most popular way that people are accessing it."

Citizens in Uruguay can grow up to five plants if they want to and there is no retail or commercial market for the drug, unlike in Canada and the US.

Dr Wilkins reckons that kind of model would work well with the green-thumbed citizens in New Zealand.

"New Zealanders have a history of growing their own cannabis and there's a lot of gardening history here so it could work, and as I said the advantage of that approach is its a really low impact market.

"People who want to grow cannabis can grow it, and it's an opportunity to reduce the black market and the gangs involved."

New Zealanders will vote on legalising cannabis for recreational use at the 2020 election, but there's little indication yet about which way it will go.

A Newshub-Reid Research poll conducted in June found 48 percent of respondents were not in favour of legalisation, which Dr Wilkins said is a change from earlier polls.

"The previous polls have all been marginally in favour but I think people are starting to really unpack this and starting to look at the consequences and they're really interested in what the options are but there's still quite a long way to go."

Dr Wilkins said he thinks people are starting to look at all the different components of legalisation and how they fit together.

"We've talked a little about the health impact, there are also criminal justice impacts... and there's economic impacts in lost tax revenue and also some employment.

"So there's a lot of different components here and there's a lot of difficult trade-offs people have got to start getting their head around."

The draft legislation will include a minimum age of 20, regulations and commercial supply controls, limited home-growing options, and a public education programme.