Canada's licensed pot producers are pushing Ottawa to exempt patients from paying any sales tax on their products, which would give medical marijuana the same tax status as prescription drugs.

The Canadian Medical Cannabis Council, a trade group representing three commercial producers, argues the tax change would allow them to compete with illegal dispensaries, which have exploded in number across the country.

Philippe Lucas, executive director of the council, said he met with a policy adviser to Finance Minister Bill Morneau during prebudget consultations last week.

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His group represents Tilray, Peace Naturals and Delta 9 Bio-Tech, which are among about two dozen commercial producers licensed to ship medical marijuana to patients through the mail.

"This is a really quick way for the current government to show that it's taking action on the cannabis file in a way that's absolutely not going to cause any backlash or controversy," Mr. Lucas, who is also a vice-president at Nanaimo, B.C.-based grower Tilray, said in an interview.

Meanwhile, more than 3,700 people have signed a parliamentary e-petition started by an employee of the country's largest licensed grower asking the government to exempt cannabis sold under the medical marijuana system from any sales taxes.

Currently, patients must pay GST and provincial sales tax or HST on marijuana and then claim the purchases as medical expenses when filing income tax. Health Canada's official position on marijuana is that it is not a medicine.

Jack Aubry, a spokesman for the federal Finance Department, no changes are planned in the near future to how marijuana is taxed.

He also said it is too early to speculate about whether the Liberal government's plans to legalize and tax recreational marijuana would affect the medical system.

"The long-standing position of the Canada Revenue Agency, which has been upheld by the courts, is that medical marijuana is not acquired pursuant to a prescription therefore sales are taxable," Mr. Aubry said in an e-mailed statement.

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Both the Ontario and B.C. colleges of physicians and surgeons say the medical document patients need to get legal medical marijuana is the same as a prescription, but Health Canada has always maintained that the drug is not an approved medicine and that it is only ensuring reasonable access to pot after being forced to by the courts.

Joanne Simons, chief mission officer at the Arthritis Society of Canada, said the federal agency approved medical cannabis as a drug treatment, so it should be subject to the same considerations as other medications.

"And that includes its tax status for users with a medical prescription," Ms. Simons said in a statement.

Her charity, which advocates for more than 4.6 million Canadians who have the condition, is preparing a report that will identify areas where more medical pot research is needed and answer important practical questions for doctors interested in prescribing the medicine.

Someone buying a gram a day at $7.95 a gram – the industry averages according to the latest Health Canada data – would pay about $410 in HST a year if they were living in Ontario.

Mr. Lucas said that is a lot of money for many of Tilray's patients, about 40 per cent of whom earn less than $40,000 a year, according to a recent internal survey. Plus, a majority of patients "don't realize that there's an opportunity to recoup some of their costs through the government," Mr. Lucas said.

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"Removing this burden right at the point of purchase is going to have the biggest positive impact [on patients]," Mr. Lucas said.

At the same time, patients across the country are avoiding the licensed system entirely and buying from illegal dispensaries.

Mr. Lucas said sales taxes are a burden to legal industry as it competes with such dispensaries – dozens of which have opened up in cities such as Vancouver, Victoria and Toronto.

It is unknown how many of Canada's several hundred dispensaries charge GST to their customers as they profit from the illegal face-to-face sale of the drug. Last month, Federal Court of Appeal judges ruled that Ottawa can collect sales taxes on any and all pot that is sold, including at illegal storefront operations, but dispensary industry insiders say the sector has no standard policy.