"The paper acknowledges that regular marijuana use increases the risk of developing depression, psychosis and schizophrenia and is especially harmful to those under 25 years old. It also acknowledges that there is a one in six chance of young people becoming dependent. This would result in further demand for mental health services," Bennett said.
Ross Bell, executive director of the National Drug Foundation, said the legal age could be one of the main sticking points.
"There are good arguments either side of this, whether it should be 18 or 20. I guess they will try to find a consensus view.
"Good public health principles would be that you want to restrict access, so that would say that 20 could be the right age.
"On the flipside of that, anything under that age is going to be illicit. That would mean that anyone under the age of 20, just as they are now, would have to buy their cannabis from the black market, so they actually miss out on any of those good public health protections," Bell said.
He also pointed out that New Zealand's youth justice system was up to the age of 18 so those aged between 18 and 20 wouldn't benefit from the protections that offered either.
Chloe Swarbrick, the Green Party's drug law reform spokeswoman, said in a tweet the leaked paper was out of date.
The referendum to legalise cannabis for personal use is part of the Labour-Greens confidence and supply agreement.
Little told the Herald he didn't know whether the leaked version was an old one.
There had been multiple versions of the Cabinet paper due to the "good and constructive discussions between the governing parties".
"There will be a paper that goes to Cabinet. When it does, and when decisions are made, everyone will be able to compare notes."
Little said the paper going to Cabinet was comprehensive and dealt with all the issues one would expect and when there was a decision it would be announced.
A poll in January showed 60 per cent of New Zealanders would vote to legalise cannabis for personal use in a referendum, 24 per cent would vote 'no', and 16 per cent had no opinion.
Almost two in three people surveyed supported a regulated market with licensed operators, while 39 per cent thought that a legal purchase age of 18 would be best.
The four options for the proposed 2020 referendum, according to the leaked paper, are:
• A general question consistent with the undertaking in the Confidence and Supply agreement: "Do you support legalising the personal use of recreational cannabis?" This would not be accompanied by any legal framework or other policy decisions and it would be left to a subsequent Parliament to determine what to do in the event of a "yes" vote.
• A questions referring to a specific policy framework document setting out the basic principles of what legalisation for personal use of recreational cannabis in New Zealand would entail: "Do you support legalising recreational cannabis in accordance with [published policy document]?" A "yes" vote would result in the duly elected Government and Parliament having some moral imperative, but no obligation, to enact law changes consistent with that policy document;
• A question referring to draft legislation that outlines the regulatory model for cannabis: 'Do you support legalising the personal use of recreational cannabis in accordance with [published draft legislation]?" Similar to option 2, a "yes" vote would result in the duly elected Government and Parliament having some moral imperative, but no obligation, to enact the legislation.
• A question referring to legislation already enacted but conditional on an affirmative vote on the referendum: "Do you support legalising recreational cannabis in accordance with the [Drug Reform] Act 20XX?" A "yes" vote would trigger the legislation coming into effect.
Bennett claimed the Coalition Government had been unable to reach a consensus and the decision around which option they would choose had been holding up the process.
"From my reading of the Cabinet paper they are highly unlikely to go with option one but I believe it's option one that New Zealand First are pushing.
"The way the Cabinet paper is written, you can kind of tell that Andrew Little probably leans to option four, so it wouldn't surprise me if they land on option three."
She said National would be pushing hard for option four.
"We believe that legislation has got time and should go through the House because of the robustness of that against public submissions. It lets select committee really get into the detail of that proposed legislation and for that to be public and everybody to get that level of scrutiny."
