It's expected details of how the referendum on legalising cannabis will be run will be taken to Cabinet next week.

Photo: 123RF

Whether to legalise marijuana for personal use is set to be put to New Zealanders at the 2020 election, as part of the Green Party's confidence and supply agreement with the Labour Party.

Photo: VNP / Phil Smith

While the specifics aren't known, Drug Foundation director Ross Bell understands Justice Minister Andrew Little will take a paper to Cabinet on Monday.

He hopes the government will make details of any decisions public next week too.

"We're only 18 months out so it would be great to have the details so that the country can start to have that important conversation and engage on the important issues around if we're going to legalise cannabis what is that going to look like.

"I think the referendum can't be a simple question of should we legalise it or shouldn't we legalise it.

"There's a whole lot of detail the public are going to want to be aware of when it comes to the important 'yes', 'no' vote", he said.

However, Mr Little has refused to comment on media speculation. The policy is working its way through government processes and an announcement will be made shortly, he said.