Toronto Mayor Rob Ford has admitted smoking crack cocaine in a "drunken stupor", despite denying he had taken the drug.
Mr Ford told reporters at city hall he had taken the drug about a year ago but was not an addict.
The mayor has rejected calls for his resignation after the revelation that a video apparently showing him smoking crack was in police possession.
He has defied calls to quit, vowing to run for re-election next year.
"Yes, I have smoked crack cocaine," Mr Ford said outside his office on Tuesday.
"There have been times when I've been in a drunken stupor. That's why I want to see the tape.
"I want everyone in the city to see this tape. I don't even recall there being a tape or video. I want to see the state that I was in."
'It is what it is'
But Mr Ford maintained to reporters that when he previously denied using the drug: "I wasn't lying. You didn't ask the correct questions."
Six months ago, the mayor said: "I do not use crack cocaine, nor am I an addict."
On Tuesday, he said: "I made mistakes in the past and all I can do is apologise. But it is what it is and I can't change the fact, and I can apologise to my family, my friends, my colleagues and the people of this great city."
The allegations of drug use surfaced in May after the gossip website Gawker and the Toronto Star reported the video's existence, but it has never been released publicly.
One city councillor has put forward a motion demanding the mayor take a leave of absence and co-operate with a police investigation, Canadian media report.
Another councillor, Jaye Robinson, told broadcaster CBC that Mr Ford no longer has "a shred of credibility".
"The real issue is getting the mayor to address his health issues, step aside [and] take a leave of absence, as I've been saying for six long months" she said.
Last week, Canadian police said they had recovered footage from a deleted hard drive that appeared to show Mr Ford smoking from a crack pipe.
Police have not revealed details of the mobile phone clip, but say it is consistent with previous descriptions from media organisations that had viewed it.
They have also not charged Mr Ford with any offence.
His friend and occasional driver Alexander "Sandro" Lisi faces charges of marijuana trafficking, possession and extortion in the wake of a broader police investigation.
Police have said they expect the video will come out when Mr Lisi goes to trial.
Earlier on Tuesday, Mr Ford's brother criticised Police Chief Bill Blair for saying last week he was "disappointed" with the mayor.
Doug Ford called the chief's comments "inappropriate" and "biased" and called on him to step aside.
Amid his disgrace, the Toronto city leader may take heart from the political comeback of Washington DC Mayor Marion Berry.
He was jailed after being videotaped smoking crack cocaine in 1990, but was re-elected to lead city hall four years later.