The group's report suggests few users of medical marijuana obtain the drug through official channels.
"Over 85 per cent of the people we consulted who used cannabis are currently relying on illegal sources for their supply of cannabis," said Lynne Bell-Isle, who worked on the 18-month project for the society.
"Only 1.7 per cent of respondents we spoke to obtained their cannabis from the government."
The federal government grows some marijuana through a private contractor, but fewer than 200 people are currently registered to receive marijuana through the program.
The report said there are several barriers to accessing the federal program, including:
- Lack of awareness of the program's existence.
- Difficulty finding doctors to support a patient's application for access.
The barriers provide an incentive to turn to the black market, the report's authors said.
Other patients are licensed to grow small amounts of marijuana for their own use.
The group noted Ottawa has invested nearly $6 million in the contract to grow medical marijauna. It calls on Canada's auditor general to investigate the program.