Canadian prime minister Stephen Harper has rallied supporters at a raucous event promoted by controversial former Toronto mayor Rob Ford, as the country counts down to a tight national election.

Key points: Stephen Harper holds rally with Rob Ford, former Toronto mayor who admitted to smoking crack

Stephen Harper holds rally with Rob Ford, former Toronto mayor who admitted to smoking crack Mr Harper is seeking re-election when Canada goes to the polls in two days' time

Mr Harper is seeking re-election when Canada goes to the polls in two days' time Liberal leader Justin Trudeau says Mr Harper should be embarrassed to count on Mr Ford's support

Liberal leader Justin Trudeau says Mr Harper should be embarrassed to count on Mr Ford's support New details of Mr Ford's drug use revealed in excerpts from new book

It was the second time in a week that Mr Harper, whose campaign has focused on law and order, rubbed elbows with Mr Ford, who gained global notoriety in 2013 after admitting he used crack cocaine while in office.

Surrounded by an estimated 1,750 cheering supporters, Mr Harper took the stage after a rousing introduction by Doug Ford, who ran for the mayor's office after his brother pulled out of the campaign to fight cancer.

"Make no mistake, God help this county, it will be an absolute disaster if [Liberal leader] Justin Trudeau and [Ontario Liberal premier] Kathleen Wynne were running this country," Doug Ford said, drawing boos with his reference to Mr Trudeau, Mr Harper's chief rival and campaign frontrunner.

Mr Harper thanked the Ford brothers and other organisers but was not seen shaking hands with either, and has not directly answered questions about why his campaign is associated with the Fords.

The prime minister's appearance with Rob Ford at two events in the final week of a close federal campaign came as new details of Mr Ford's alcohol and drug abuse in office were revealed in excerpts from a book by a former aide, Mayor Rob Ford: Uncontrollable.

The former mayor and his brother remain Conservative Party stalwarts who wield considerable influence in Toronto's suburbs, where their populist low-tax message has many supporters.

Mr Ford made global headlines by refusing to resign as mayor even after he admitted he had smoked crack while in a "drunken stupor".

The Fords "appeal to lots of people in the Toronto suburbs who feel the elites don't speak for them", said Robert Drummond, political science professor at York University.

"I think it is not a smart move, but I suspect the PM would prefer not to have the Fords opposing him because he wouldn't come to their rally."

Mr Trudeau told reporters in Montreal that Mr Harper should be embarrassed to count on Rob Ford's support.

But Mr Ford's backers were more forgiving.

"Whether I agree with their past behaviour, I can't say I do," said Arnold Birnie.

"You don't have to be a Liberal to smoke dope and get addicted and make mistakes."

Reuters