The newly-released Massey University drug report shows methamphetamine is more easily accessible than cannabis in New Zealand.

When asked about availability, 14 per cent of cannabis users rated it as "very easy", while 54 per cent of meth users said the same.

Just 14 per cent of cannabis users could buy the drug within 20 minutes, while 31 per cent of meth users could do so.

Dr Chris Wilkins of Massey University said it comes down to supply.

"In the southeast Asian region there's a lot of production of methamphetamine and the reality is that's just flooding in to New Zealand," Dr Wilkins told TVNZ 1's Breakfast.

"Cannabis, you have to grow it for two-three months, it's a very bulky drug, it has a distinctive smell so it's just [that] methampehtamine probably looks like a better option [for suppliers] in terms of concealment and being able to sell that drug."

Dr Wilkins noted that a lot of respondents to the survey said they would prefer to use cannabis, but were unable to get it, so used methamphetamine instead.

He was surprised to find the survey showing meth usage was highest outside of the main urban centres.

"It may well be that there are less job opportunities, more poverty, but also some of the places like Bay of Plenty has a large port so it's a natural part for smuggling, and Northland also has a coastline where a lot of methamphetamine is being seized, so those are all factors as well," Dr Wilkins said.

Some may be choosing meth over cannabis because meth stays in the body for a shorter time - a consideration when undergoing work drug testing.

Dr Wilkins said the report suggests police should be re-assessing how much resource they put into cannabis enforcement, and said there may need to be a "re-balancing" back towards meth.

"People could ask some really interesting question about how they want to spend their taxpayer dollars in terms of drug enforcement - is it on cannabis, or should it be focused on methampethamine only?

"For cannabis it seems to me they're in the ballpark of alcohol and tobacco, and we could really be doing something a bit more innovative than arresting people.

"The government has signaled they are going to have a referendum on cannabis by 2020, and I think that's a really good opportunity for New Zealanders to sit down and think about the issues and decide where they want to go with cannabis.