Toronto Mayor Rob Ford, who gained global notoriety for admitting he smoked crack cocaine, dropped his re-election bid, citing a health crisis, but his older brother took his place in the race to run Canada's largest city.

The family switch was made minutes before a deadline for changes to the city election ballot, which also saw a Ford nephew withdraw to allow his uncle, the mayor, to run for a city council seat in his place, reports Reuters on Friday.

The October 27 election is seen as a referendum on Ford's four tumultuous years leading Toronto, as recent polls had shown him in second place in a tight three-way race.

Doug Ford, the mayor's older brother and campaign manager, is regarded as less charismatic but less volatile than his larger-than-life sibling, who steadfastly refused to resign even as he admitted buying illegal drugs while in office and checked himself into rehab.

"My heart is heavy when I tell you I am unable to continue my campaign for re-election as your mayor", Rob Ford said in a statement, adding that he could be "facing the battle of my lifetime".

"I've asked Doug to finish what we started together so that all we've accomplished isn't washed away. I've asked Doug to run to become the next mayor of Toronto because we need him."

The 45-year-old mayor was admitted to hospital on Wednesday after complaining of unbearable abdominal pains and was diagnosed with a tumour. He is undergoing a battery of tests, with biopsy results expected in a week.

At a press conference on Friday evening, an emotional Doug Ford said that it had been a difficult few days for his "close-knit" family and in particular for his brother, who did not take the decision to step down from the mayoral race lightly.

"This is more than a job for Rob, it's his life's work and his passion to fight for this city, and for each and every one you," Doug Ford told reporters. "He told me that he needed me to take the torch while he focuses on getting better."

A 49-year-old businessman, Doug Ford was elected as a city councillor in 2010 when his younger brother became mayor.

Source: Reuters