Prime Minister John Key says decriminalising cannabis would send the wrong message to young people - and he isn't keen on holding a referendum on the issue.
A new poll shows almost 65 per cent of New Zealanders want personal possession of cannabis decriminalised or made legal.
There is even stronger support to let people use cannabis for pain relief - only 16 per cent of New Zealanders want that to be criminal.
Speaking at his post Cabinet press conference yesterday, Key said his view was changing the law would send the wrong message to younger people.
He did not back a referendum on the issue, and pointed to the recent outcry over shops selling "legal highs" or synthetic cannabis products, before the Government stepped in.
Some Australian states have civil fines - similar to speeding tickets - instead of criminal penalties, and that has not led to cannabis being sold from stores.
"Police always have the right to exercise discretion, and do...you come back to that question of do we want to see increased drug taking in New Zealand? Personally, I'm of the view that we don't."
The results of the new poll come just months before the Government embarks on a review of the offence and penalty regime for personal possession.
Debate about cannabis reform has been stirred by former union leader Helen Kelly and the late Martin Crowe using the drug for medicinal pain relief, and new approaches taken overseas including in Australia.
Kelly, who has terminal lung cancer, said this morning the Government should act now.
"New Zealand has the highest rate of prosecution for cannabis possession in the OECD and targets young people, it is discriminatory in terms of ethnicity [and] who is getting prosecuted," Kelly told Radio New Zealand.
"People who are using it for medical purposes are still getting prosecuted in this country. It's not true that police are turning a blind eye...I think we need to look at the whole system, and start with medical, see how that works...and then see where the gaps are and look at who is being prosecuted, and why."
Labour has indicated it could hold a referendum on decriminalising cannabis and National will shortly review how harshly people are dealt with for low-level drug offences.
Current penalties range from a $500 fine for possession to a 14 year jail term for its supply and manufacture. Cultivation of cannabis can result in a 7 year jail sentence.
The Drug Foundation commissioned the polling.
Ross Bell, the foundation's executive director, said the results should embolden politicians.
"This isn't the scary beast that it may have been, even two or three years ago.
"Support for reform is now a majority position. In past polling we have seen it has been in the minority or evenly split. Now it has tipped over."
People polled were asked if an activity should be legal, illegal and subject to criminal penalties, or illegal but decriminalised - an offence punishable by a fine, with no criminal record.
Sixty-four per cent thought personal possession of a small amount of cannabis should be either be legal or decriminalised.
That fell to 52 per cent on personal growing of cannabis, 30 per cent for selling from a store, and just 21 per cent for growing for friends.
The strongest support was for reform in relation to cannabis use for pain relief (79 per cent either legalise or decriminalise) and terminal pain relief (82 per cent).
The Drug Foundation, which receives government funding and has a stated aim of preventing and reducing harm from drug use, wants cannabis use to be treated as a health problem.
The foundation favours the approach taken by Portugal, where drug users were assessed by health professionals and referred to treatment.
In a similar poll by a different polling company two years ago, 32.3 per cent thought smoking cannabis should attract a fine but not a criminal conviction; 20.3 per cent thought it should be legalised; and 44.8 per cent thought it should remain illegal.
A spokeswoman for Health Minister Dr Jonathan Coleman referred questions to Associate Health Minister Peter Dunne, who said the Government had been clear on its position - that leaf cannabis would remain illegal.
However, an adjustment of how severely people are dealt with for drug offences is possible with two reviews pending.
As part of the 2015-2020 national drug policy, the Government is reviewing the regulation of drug utensils, including associated penalties.
And next year the penalty and offence regime for personal possession of drugs will be reviewed.
Asked if that could consider fining people for personal possession of cannabis, or referring them to a health service, Dunne said it was premature to speculate, "but any review opens up a range of possibilities".
In the past, he has highlighted three words - compassion, innovation and proportion - as underpinning the national drug policy.
Labour leader Andrew Little last week told a student radio station that Labour could hold a referendum on such a move, but later downplayed the comments.
Police already employ practices such as pre-charge warnings to divert low-level drug offenders away from the criminal justice system, but Bell said this was applied unevenly, with Maori less likely to benefit.
Conservative lobby group Family First rejected calls for the law around cannabis to be changed, saying the new polling showed "New Zealanders don't want a free-for-all".
"This poll confirms that the public are nowhere near settled on this issue - and they are right to be cautious," said Bob McCoskrie, national director of Family First NZ.
The NZ Drug Foundation commissioned the recent polling by Curia Market Research, the company owned by National's pollster David Farrar.
The poll of 1029 respondents ran from July 18 to August 2 and has a margin of error of 3.1 per cent.
The poll two years ago was part of a Herald-DigiPoll survey of 750 people and had a margin of error of plus or minus 3.6 per cent.