Toronto's former chief planner is blasting the multi-billion dollar rebuild of the eastern Gardiner Expressway as "frivolous spending."

Jennifer Keesmaat made the comments while discussing how the city should pay for public transit on CBC Radio's Metro Morning on Monday.

Council narrowly approved building a "hybrid" version of the elevated expressway — one championed by Mayor John Tory — in 2015. That option was more expensive than bringing the highway down to ground level, and could cost some $2.3 billion.

"Absolutely it was the wrong decision. It was frivolous spending," said Keesmaat.

In so many cities, we have a big debate - and a user fee - when it comes to funding transit. But building new highways and roads? We assume the general tax base should pay for that. We need a new model that incentivizes what we want most: efficient mobility, sustainable choices. —@jen_keesmaat

Tory, who went to a Pape Avenue bakery to reannounce the city's plans to roll out two-hour transfers on the TTC, is defending the decision. He said council's choice was made in "best interest of the city."

The mayor gave no indication that the city would be reconsidering the plan, even with Sidewalk Labs, a sister company of Google, pitching a pedestrian-friendly development for the section of waterfront adjacent to the highway.

The mayor says the hybrid option features "substantial changes" that free up waterfront space while still maintaining the ring road.

However, he admits some people still take issue with the design and noted Keesmaat has been consistent in her criticism.

Back in 2015, Keesmaat was a strong supporter of converting the 1.7-kilometre stretch of elevated expressway into a grand boulevard.

She argues the money saved could bolster transit service that tens of thousands rely on, at little expense to the some 5,500 cars and trucks that take the Gardiner every day.