Sixty per cent of those asked said they would vote "yes", 24 per cent would vote "no", and 16 per cent had no opinion.
The strongest support for legalisation came from the 25 to 34 age group (75 per cent), while the only age group that did not show majority support for legalisation was the 65 and over age group.
The survey also asked about a regulatory framework around legal cannabis:
• 63 per cent wanted a regulated market for legal cannabis with licensed operators
• 39 per cent wanted the legal age to buy cannabis to be 18; 36 per cent supported 21; 32 per cent said if the legal age was set too high, it would lead to a black market
• 58 per cent said penalties for breaking the law in a legal cannabis market should be about the same for breaking the law on alcohol sales; 28 per cent supported severe penalties
•18 per cent supported the Government owning and controlling all production and sale of cannabis
• 40 per cent wanted a Government excise tax, and 68 per cent said any tax revenue should go towards health services
An independent economic analysis commissioned by the NZ Drug Foundation last year found that a legal, regulated market for the purchase of cannabis would bring $185m to $240m in new tax revenue, and that putting $150m a year back into health services would see wider societal benefits equating to about $225m a year.
The latest survey also saw a clear majority - 55 per cent - saying they had used cannabis at some time, while 10 per cent said they used it daily.
That would equate to about 340,000 adults using cannabis daily, much higher than other surveys. Daily use was most prevalent among people aged 18 to 24 (22 per cent) and among those earning $20,000 a year or less (30 per cent).
NORML NZ, which advocates for marijuana law reform, puts the daily user number at around 70,000 (from a 2010 Horizon survey) , while the Ministry of Health 2012/13 cannabis use survey showed only 3.8 per cent of adults aged 15 and over used cannabis on a weekly basis.
Sixty per cent of those in the latest survey said they believed legal cannabis would result in lower levels of crime, or have no effect, while about a third said it would reduce harm and a quarter said it would increase harm.
The survey also asked about medicinal cannabis, and found 81 per cent support.
The Government last year passed a law for medicinal cannabis and this year will be consulting the public on the regulatory framework.
Helius executive director Paul Manning said the jump in reported daily users might be because cannabis use is becoming more mainstream, leading to people sharing their actual usage habits.
He said Helius was focused on medicinal cannabis products, but the survey results were encouraging and legalising cannabis for personal use would change the market.
"If New Zealand follows a similar path to Canada, where both medical and recreational sales are permitted, we will see the total domestic market for cannabis-based products expand significantly," says Mr Manning.
"Although we have no plans to operate in the recreational space, the referendum could open up the opportunity to offer New Zealanders a wider variety of cannabis-based wellness products, such as functional foods, beverages and cosmetics."
The latest Horizon results were from a nationwide survey conducted in October of 995 adults 18 and over, and weighted to be representative of the population at the 2013 census.
The margin of error is 3.1 per cent.
