Montreal Mayor Gérald Tremblay has challenged his Projet Montréal rival Richard Bergeron to detail how the city would survive economically if his vision of a carless city became reality.

Tremblay attacked his fellow mayoral candidates during a debate on environmental issues Tuesday night at the Unversity of Quebec at Montreal's Sherbrooke Pavillion.

Tremblay touted his administration's green record, while rival Louise Harel and Bergeron took turns criticizing his claims.

Harel attacked Tremblay's decision to approve a controversial residential project on the site of the old Marianopolis College, located on the south bank of Mont Royal Park.

That kind of development would never be approved in New York City's Central Park or Hyde Park in London, Harel said.

Bergeron reproached Tremblay for approving the creating of 25,000 new parking spots in downtown Montreal over the last three years.

Tremblay dismissed the criticism as rhetoric.

"Richard Bergeron wants to eliminate all cars on the island of Montreal. That's impossible. And before we can even start reducing considerably the number of cars, we have to find the solutions," he said.

"You can't eliminate all the trucks on the island of Montreal. We have a port in Montreal and that creates thousands of jobs. [Bergeron's] proposal is to close part of the port, and that's 22,000 jobs that'd be lost in the eastern part of Montreal. So, when it comes to reality, you have to balance the advantages and the inconveniences," Tremblay said.

No one wants more smog and congestion on the island, he added, but solutions have to go hand in hand with economic development or there will be no way to pay for them.

The debate was hosted by Montreal's Conseil Régional Environment.

Montreal will elect a new mayor on Nov. 1.