Toronto conservative mayor Rob Ford has admitted that he smoked cannabis during a debate on legalising the drug in Canada.

Ford, 44, was asked if he had used pot after a series of high-profile politician went public on past drug use.

"Oh yeah," Ford told reporters. "I won't deny that. I smoked a lot of it."

Earlier this year Ford was allegedly caught on camera smoking crack cocaine. The video secretly recorded by drug dealers was never released. Ford denied the allegations.

Canada's debate over drug policies has been building since Liberal party leader Justin Trudeau called marijuana to be legalised.

Trudeau sparked controversy by saying he last had a "puff" of marijuana at a dinner party three years ago, while serving as an MP.

"I have not taken other drugs. I have been a very rare user of marijuana, I think five or six times in my life I've taken a puff - it's not my thing. I think I'm in more trouble for admitting that I don't drink coffee on social media today," Trudeau later elaborated.

Prime Minister Stephen Harper said he had never smoked marijuana and added that he had asthma but Trudeau's remarks opened the gates to the outing of several other politicians.

Ontario's premier, Kathleen Wynne, said she smoked "a little pot" 35 years ago and opposition leader Tom Mulcair said he had smoked marijuana but the last time was before he was elected.

According to a June 2012 Ipsos-Reid poll, 66 percent of Canadians support either decriminalisation or legalisation of marijuana.

Across the US border, the states of Washington and Colorado recently legalised the use of cannabis.

Canada's ruling maintained that marijuana should remain banned because of drugs' "harmful effect on users and on society".