Toronto Mayor John Tory is "tragically wrong" to want to keep the eastern Gardiner expressway, warned former mayor David Crombie, who is urging his old friend to reconsider.

Mr. Crombie remains a well-regarded figure in Toronto, decades after leaving office, and was one of the highest-profile endorsements Mr. Tory secured on his campaign to victory last year. But the man once known as the "tiny, perfect mayor" said Mr. Tory is making a big mistake in backing the elevated highway.

"He's a good man and I hope he listens to what's being said," Mr. Crombie told reporters Monday. "Rebuilding the elevated Gardiner Expressway of 60 years ago is building the city for yesterday."

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The former mayor – who was instrumental in stopping the Scarborough Expressway in the 1970s – said the Gardiner East debate was about Toronto ensuring "we are part of the 21st century and not simply riding in the 20th."

His remarks came the same day as the release of a poll showing that taking down the eastern Gardiner was the preferred option in every age group and region of the city, as well as among both men and women.

What to do with the Gardiner east of Jarvis is the biggest decision to face this council.

Rebuilding it in essentially the same form – the option often dubbed "the hybrid" – will cost $919-million over the life cycle of the road, while replacing the elevated highway with a boulevard would cost $461-million over the long term. Keeping the highway elevated will save a few minutes for a small group of motorists, according to the city's environmental assessment, but open up less city land for development.

City politicians are due to debate the issue at next week's council meeting. But downtown councillor and deputy mayor Pam McConnell hinted Monday that the debate could end up being deferred. She said that she would be ready to take more time to make a decision on the Gardiner East if that would allow for a broader consensus on the issue.

"We have to make the right decision, and I think right now it's an emotional decision that people are making that is not based on the facts," she said. "So if I can get some time for people to digest those facts, I'm perfectly happy to do that."

While guest-hosting a radio show earlier Monday, Mr. Tory reiterated his support for keeping the Gardiner elevated, arguing that he wasn't elected to increase congestion. His spokeswoman took to Twitter to criticize the new poll for using questions that, while they described the Gardiner options, didn't refer to keeping it up as the hybrid, the name preferred by advocates of that choice.

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Mr. Crombie was joined by former chief city planner Paul Bedford and Ryerson University President Sheldon Levy, both of whom argued for the boulevard option. Mr. Levy, who served on the mayor's transition team, made his case using language reminiscent of the argument made by then-premier Bill Davis when he cancelled the Spadina Expressway in 1971.

"Choosing people before cars," Mr. Levy said. He cited some of the other cities that have removed elevated expressways and added: "No one was ever sorry they made that decision to tear it down."