Canadians are embarking on a "bold new world" aiming to legalise recreational cannabis.

Criminal penalties for the possession, use and social supply of all drugs - not just cannabis - should be scrapped, the Drug Foundation has proposed.

It announced the policy on Wednesday at its Parliamentary symposium, also calling for a strictly regulated cannabis market and more resources for prevention, education and treatment.

Current laws were making criminals out of people when harmful drug use needed to be treated as a health issue, said policy author Kali Mercier.

Under the Drug Foundation's policy, the commercial supply and trafficking of drugs would still be punished, but people who were caught with drugs for their own use would not face criminal penalties.

It was similar to the Portugal model, which the foundation said had produced early positive evidence of reduced drug use, fewer offenders in prison, fewer court cases and a reduction in HIV infections and overdoses.

The Drug Foundation's proposal would remove criminal penalties for personal use of cannabis and other drugs.

Under the foundation's model, if police found a person in possession of drugs, they would issue a "mandatory caution" and also give that person health information and legal advice.

"After one, two or three cautions (depending on the drug), the person would be required to attend a brief intervention session run by a community alcohol and drug treatment service.

"The session would result in a recommendation as to whether further health assessment and treatment is needed. If so, a range of non-compulsory treatment options would be available."

Former Canadian Health Minister Anne McLellan is chairing a Government taskforce in her country to advise the Government on how to regulate cannabis.

Any legal penalty for not attending the brief intervention session would be restricted to an option to reschedule or a low fine.

Speaking separately to the symposium, Prime Minister Bill English said he supported ongoing discussions, but the Government had no plans to decriminalise or relax drug laws.

"In New Zealand we've always taken the view that some of these drugs cause so much harm, that they should be illegal."

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Cannabis was one of those drugs, in English's view. He did not buy arguments that current laws were not working.

"I think those arguments should be listened to, but the case hasn't been made."

'HORRENDOUS' RISKS OF REFORM

Earlier in the conference, a Canadian expert outlined some of the risks of legalisation, which has been pursued in her country.

Dalhousie University Chancellor Anne McLellan said without relentless and "aggressive" public education programmes, any mistakes made in the legalisation of cannabis would be "horrendous". But that did not mean the status quo should remain, she said.

"Public education is going to be key here - absolutely key. And one of the things we heard in places like [US states] Washington and Colorado was that you begin your public education campaign as soon as possible," McLellan told delegates.

"You don't wait for legalisation, how crazy would that be?"

McLellan is the chair of a government taskforce to advise on how best to regulate and restrict cannabis use, as the Liberal Government under Prime Minister Justin Trudeau moved to legalise by July, 2018.

She is also a former Canadian Prime Minister, and Health Minister, who held the portfolio at the time Canada legislated to allow the use of medicinal cannabis and the only legal grower was the Canadian Government.

McLellan said they quickly learned the Government should not be in the business of growing. The innovation, risk-taking and development of a regulated cannabis market was better handled by the private sector.

Like New Zealand, cannabis was the most-used illicit substance in Canada and outpaced tobacco use in younger people. That was partly due to heavy restrictions in marketing and advertising for tobacco, "and aggressive public education", which had seen its use drastically reduced in recent years.

Canada was also looking at measures like plain packaging to deter people from being enticed to start a cannabis habit.

Heavy usage and usage from an early age was known to have harmful and permanent effects on developing brains, which medical research suggested was up to 24 years of age.

"So early usage and heavy usage are not desired outcomes, by any means," McLellan said.

But because it was known that cannabis usage rates were high in both countries, even though there was a substantial illegal market, it was clear that important social outcomes were not being recorded.

"There's no control over product safety, there's no nice labelling you buy from the dealer on the corner street outside a local school. No quality control, no information about potency, no information about fertilisers that might have been used or other substances to grow the product."

The Canadian model was also focused on stamping out illegal elements of the drug trade - in particular, the supply and distribution through major gang operations.

"My goal, after 10 years, would be to have 80 per cent of organised crime out of the cannabis business - an incredibly ambitious target," McLellan said.