Stephen Harper says revelations that Liberal Leader Justin Trudeau smoked marijuana even after being elected to Parliament "speak for themselves."
Mr. Trudeau revealed in an interview this week that he used pot three years ago. He won a seat in the Commons in the 2008 election.
"For Mr. Trudeau, I think those actions speak for themselves and I don't have anything to add," Mr. Harper told an audience in Rankin Inlet, Nunavut, during the latest stop on his annual summer tour of northern Canada.
The Prime Minister paused after being asked a question about Mr. Trudeau's cannabis use. He stopped, took a drink of water, and cleared his throat before answering in a manner that suggested he was disdainful of Mr. Trudeau's conduct.
The Liberal Leader told the Huffington Post he last smoked marijuana about three years ago at his house in Montreal. "We had a few good friends over for a dinner party, our kids were at their grandmother's for the night, and one of our friends lit a joint and passed it around. I had a puff," he told the online news site.
When reporters asked Mr. Trudeau about it in Quebec City, he expressed no regrets.
"No, it wasn't a mistake," he said. "...I've never tried other types of hard drugs. I am not a consumer of marijuana but, yes, I've already tried it. I used it — maybe five or six times in my life."
Mr. Trudeau said he believes public opinion has moved on and he's confident that Canadians will judge him less harshly than his political opponents.
Justice Minister Peter MacKay said Mr. Trudeau showed a "profound lack of judgement."
"By flouting the laws of Canada while holding elected office, he shows he is a poor example for all Canadians, particularly young ones," Mr. MacKay said in a statement.
Mr. Harper and Mr. Trudeau have already locked horns over marijuana. The Liberal Leader proposes legalizing pot use and his Conservative rival flatly rejects both legalization and decriminalization of it.
Mr. Trudeau's admission comes after all three major party leaders were asked by the Huffington Post when they had last smoked marijuana. Mr. Harper said that he had never smoked pot, citing his asthma condition. NDP Leader Thomas Mulcair, meanwhile, told the website that he has smoked marijuana in the past, but declined to say when.
In the interview, Mr. Trudeau said that legalization would help keep the drug away from criminal groups and children, and expressed support for placing limits on tetrahydrocannabinol levels – the active intoxicant in marijuana – in what could be sold to the public.
NDP justice critic Françoise Boivin criticized Mr. Trudeau for only recently reversing his stance on legalization.
"The NDP has for decades consistently said that no one should go to jail for simple possession of marijuana," Ms. Boivin wrote in an e-mailed statement.
With files from Bill Curry in Ottawa, Ann Hui in Toronto and Canadian Press