Federal figures show the annual Mountie-led effort, known as Operation Sabot, has led to tens of thousands of pot plants being weeded out each year.
Liberal defence critic Joyce Murray, who uncovered the data, said she was "stunned" to see the amount spent on the project — especially when many are calling the war on drugs a failure.
The RCMP says the goal is to target outdoor marijuana growers and reduce the supply of pot available in Canadian communities.
"The success of Operation Sabot means that less marijuana is available for sale in our communities," said RCMP Sgt. Greg Cox, a spokesman for the national police force.
"These drugs could ultimately have been sold to youth and adults alike, and the profits used to finance organized crime."
Last year the military spent more than $361,000 on helicopter support for the operation, which resulted in eradication of over 40,600 plants.
The military put more than $2.5 million toward the project in 2009 — the highest annual tally among the figures disclosed to Murray through a parliamentary order paper question. That year 145,480 plants were destroyed.
Operation Sabot has taken place annually since 1989, according to information on the Defence Department website. However, the numbers tabled in Parliament date only from 2006.
Over the years, as many as seven Armed Forces helicopters, three ground vehicles and 60 military personnel have helped with the operation.
The total cost of well over $11.4 million for 2006 through 2013 includes only military air support. Other military and RCMP expenditures could not be easily calculated.
The Defence Department indicates that efforts focused on Ontario and Quebec last year.
Cox declined to say when — or in which provinces — this year's operation would take place. But he said the Mounties remain committed to working with the military on the anti-pot mission.
Murray questioned the exercise's value, arguing the best way to tame the criminal marijuana trade is government regulation of the drug, as two American states — Colorado and Washington — have done.
"I think it's inevitable we'll go that direction," she said in an interview.
Liberal Leader Justin Trudeau has advocated legalizing marijuana, placing it under government regulation, as a means of safely controlling access to the drug.
The Conservative government says it has no intention of decriminalizing marijuana. However, Justice Minister Peter MacKay said this week the government is still assessing whether to allow police to ticket people caught with small amounts of pot instead of pursuing charges.
The fact the Tories are pondering the option is telling, Murray said.
"I think that they're also recognizing that prohibition just hasn't worked."
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