On a day of political crises that began with a police chief under fire and a city council threatening to curtail the mayor's power, Rob Ford admitted that he has indeed smoked crack cocaine.

Even by the standards of a city government that has been rocked by a series of unsavoury allegations, from the existence of a crack video to extensive police surveillance of the mayor's activities, Tuesday was extraordinary.

Related: Watch a video of from Mr. Ford's afternoon press conference

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Councillor Doug Ford was on radio and TV accusing Toronto Police Chief Bill Blair of leading a politically motivated attack on his brother, after the chief said last week he was disappointed in the mayor. Meanwhile, the mayor was at a Toronto Community Housing building looking into complaints about bugs. The mayor then drove to City Hall and with little warning to his team, sources say, brought six months of speculation to a surprising conclusion.

"Yes, I have smoked crack cocaine," Mr. Ford said.

Related: Watch a video of Mr. Ford's admission

Although the allegation had simmered for months, the revelation still left many shocked. The reverberations were both immediate and wide-ranging. Ontario Premier Kathleen Wynne said she was alarmed by the turmoil at City Hall. Canada's Justice Minister Peter McKay called it a sad day for Toronto and urged the mayor to get help. City councillors on both sides of the divide strategized over how to either limit his powers or force him to explain himself.

Many observers struggled to answer the question: what next?

In open conflict with Chief Blair, with a council scrambling to free itself from what it perceives as the mayor's sinking ship and with his allies urging him to take leave, governing Canada's largest city is likely to prove difficult.

But Mr. Ford remained defiant, vowing to stay in the job and seek re-election in 2014. In prepared remarks delivered late in the day, an apologetic and at times emotional Mr. Ford said that he felt as though a thousand-pound weight had been lifted from his shoulders.

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"I know what I did was wrong. And admitting it was the most difficult and embarrassing thing I have ever had to do. Folks, I have nothing left to hide. I would do anything – absolutely anything – to change the past. But the past is the past and we must move forward," he said. "I was elected to do a job, and that's exactly what I'm going to continue doing."

The news lit up websites around the globe, as the BBC, CNN and others gave the story huge prominence.

The drama began shortly after sunrise when the mayor's brother escalated his attacks on Chief Blair. In a series of interviews, Councillor Ford called on the chief to resign, accusing him of bias for expressing "disappointment" with the mayor.

"[Chief Blair] wanted to go out and put a political bullet right between the mayor's eyes and thought that would be the final bullet to knock the mayor off," Councillor Ford told AM 640 radio.

The accusations were a stunning broadside against the police chief and raised the prospect of a dangerous rift at the heart of civic government. Some councillors expressed astonishment at the councillor's aggressive tone. The chief's spokesman said only that the police enforce the law without fear or favour. Shortly after, Councillor John Filion brought forward a motion that would curb the mayor's power to appoint or fire members of his executive. Then the mayor dropped his bombshell.

Within minutes, Ms. Wynne spoke to the press. According to sources at Queen's Park, the Premier has received legal advice on the levers she might exercise to restore order, but for the moment is watching and taking her cues from Toronto's council.

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As word leaked that the mayor would be making another statement later in the afternoon, the expectation was that he would announce either his resignation or a leave of absence. But the mayor was in a combative mood, according to sources.

When he emerged to speak to reporters around 4:30 p.m., he appeared contrite and embarrassed, but determined not to buckle.

"These mistakes will never, ever, ever happen again. I kept this from my family, especially my brother, Doug, my staff, my council colleagues because I was embarrassed and ashamed. To the residents of Toronto, I know I have let you down. And I can't do anything else but apologize and apologize and I'm so sorry."

Councillors struggled to predict what will happen as the ranks of Mr. Ford's allies continue to thin, leaving the mayor and his brother increasingly isolated.

Some, such as Karen Stintz, who has declared her intention to run for mayor next year, suggested the crisis is limited to Mr. Ford's office.

Others said the events of the past week have changed everything. "I don't actually see how … you put the genie back in the bottle," said Michael Thompson, a member of the mayor's executive committee.

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At the very least, several councillors questioned how the mayor and his brother can have any involvement in the approaching police budget discussions given that the mayor is refusing a request to be interviewed by the police and Doug Ford is calling for the chief's resignation.

No one can force the mayor to step aside, but Mr. Ford will face two separate initiatives from council, beginning at next week's meeting. The first, spearheaded by councillors Denzil Minnan-Wong and Peter Milczyn, asked him to apologize and take a leave.

The motion needs the support of two-thirds of council, but even if it gains support, the mayor has shown no sign that he would heed it. Indeed, Mr. Milczyn said he received a call from a member of the mayor's staff Tuesday suggesting his position as chair of the city's planning committee and his place on the mayor's executive would be "at risk," if he went through with the motion – suggesting the mayor is preparing for a fight.

The second initiative, spearheaded by Mr. Filion, would be debated at council's meeting in December and would change the rules to temporary place limits on the mayor's power to appoint and dismiss the deputy mayor and the chairs of the city's standing committees.

Mr. Filion, a critic of the mayor, said the move gives the mayor two choices, work with the people he has appointed or hold up in his office. "The train wreck is in sight. This repairs the tracks so it doesn't happen," he said.

With reports from Adrian Morrow, Josh Wingrove and Kaleigh Rogers