OTTAWA — The federal government will learn Friday whether it may have to cough up billions of dollars in health-care costs stemming from smoking-related illnesses.

The Supreme Court of Canada will determine if the federal government can be a third-party defendant in a lawsuit against tobacco companies and, by extension, bear some financial responsibility for the costs provinces incurred to care for ill smokers.

Four provinces — B.C., Ontario, New Brunswick and Newfoundland and Labrador — have launched lawsuits against tobacco companies for past, present and future health care associated with tobacco use. Four more have announced intentions to launch lawsuits of their own.

The case before the Supreme Court stems from a lawsuit originally filed 10 years ago in B.C. from smokers over the sale of light and mild cigarettes, which they argue were inaccurately marketed as being less of a health risk than regular cigarettes.

B.C. has not said how much it could ask for in costs, but Ontario is suing tobacco companies for $50 billion.

With so much money at stake, the tobacco industry has argued that the federal government was a key industry researcher, regulator and adviser, which makes Ottawa partially responsible for any ailments related to smoking.

The government argued that the point of the lawsuits was to recoup money for provincial taxpayers and shouldn't be "frustrated by allowing the tobacco industry to pass those costs back to taxpayers through another level of government."

Allowing Ottawa to be a third-party defendant would also "make Canadian taxpayers the effective insurers of all risks relating to the defendant's tobacco products," the government wrote in its submission to the court.

The B.C. Court of Appeal ruled in 2009 that the federal government could be named as a third-party defendant in the massive lawsuit.

At the time, Imperial Tobacco, one of the companies named in the B.C. lawsuit, said it was satisfied with the ruling. On Thursday, company spokesman Eric Gagnon said the company was hopeful to see the Supreme Court uphold that ruling.

Imperial Tobacco argues that Agriculture Canada developed and advised the industry to use its tobacco for light and mild cigarettes, all while collecting billions in tax revenue.

"If (Imperial Tobacco) committed wrongful acts that in law caused the province to incur recoverable health care costs, then so too did Canada and Canada should face liability to the degree of its own fault," the company writes in its court submission.

"We don't agree with that," said Rob Cunningham, a lawyer with the Canadian Cancer Society, which has watched the case from its beginnings.

"They (tobacco companies) should pay and not try and blame somebody else, which is a long-standing tactic of the tobacco industry."

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