Canadian Prime Minister Stephen Harper told reporters that marijuana is "infinitely worse" than tobacco — a claim that was widely dismissed by public health experts.

The comment was made at a press conference on Saturday, after the final federal leaders' debate of the Canadian election, in which Harper criticized the Liberal party's policy of legalizing and regulating the sale of pot.

"There's just overwhelming and growing scientific and medical evidence about the bad long-term effects of marijuana," he said, answering a reporter's question on his opposition to marijuana despite its legal medicinal use and the fact that alcohol and tobacco are regulated.

"We've spent a couple of generations trying to reduce the usage of tobacco in Canada with a lot of success," Harper continued.

"Tobacco is a product that does a lot of damage, marijuana is infinitely worse, and is something we do not want to encourage, obviously."

He then reiterated the Conservative party's stance on drugs: treat people with addictions, but maintain tough laws against traffickers, "who profit off of destroying people's health."

Dr. Dan Werb, director of the Toronto-based International Centre for Science in Drug Policy, says Harper is only half-right — tobacco is very dangerous.

However, after a lifetime of use, less than 1 in 10 of all marijuana users are estimated to become addicted, while over two thirds of nicotine users become addicted over a lifetime of use, he says, adding that on a range of metrics, including short and long-term cognitive impairment, and risk of death, marijuana is consistently shown to be less harmful than drugs like alcohol and tobacco.

"With respect to the notion that regulation encourages drug use, would the prime minister suggest that Canada's tobacco regulation system encourages tobacco use?" Werb asked. "The opposite is actually the case — the annual rate of smoking among Canadians has been dropping steadily for the past two decades, with the highest decline among youth aged 15 to 19 years old."

If the Canadian government hopes to reduce drug use, especially among youth, it should take lessons from the success of the regulation of tobacco, he says.

"The deaths from tobacco use are equal to three times the amount of all the deaths from the following things — cannabis use, other illicit drug use, homicides, traffic accidents, alcohol and HIV aids," says Robert Schwartz, the director of the Ontario Tobacco Research Unit.

Although he says cannabis use isn't benign — it affects brain development in users younger than their early 20s, can impair driving, and affect motor function and cognition in daily users — Schwartz points to the Toronto-based Centre for Addiction and Mental Health (CAMH) framework on cannabis documenting, which draws a comparison between alcohol, tobacco, cannabis and other illicit drugs.

On CAMH's scale, which goes from 0 to 100, tobacco receives 100 on its effect on physical health, and cannabis receives 20.

Liberal party leader Justin Trudeau has said he'd legalize marijuana "right away," although he didn't provide details on how the drug would be taxed or exactly when it would be legalized.

Although NDP leader Thomas Mulcair called Trudeau out in September for his admission that he'd smoked weed "maybe five or six times in his life," he committed to decriminalizing marijuana "the minute we form government."