A Toronto councillor has obtained a legal opinion that concludes Mayor Rob Ford does not have the power to cancel the Transit City plan without City Council's approval.

Debate over how Toronto should invest billions in upcoming transit improvements has flared up in recent days, with several councillors pushing for Ford to back down from his position that a planned Eglinton Avenue light-rail line should be built below grade.

As originally conceived under David Miller’s Transit City plan, the Eglinton line was supposed to be buried only along the busiest stretches of the road. But Ford has long been insistent that the Eglinton line must be underground, a scenario that raises the cost of the project considerably and has led critics to question if that is the most practical option.

The mayor pushed hard on the issue from the outset of his term, declaring Transit City “over” and eventually signing a memorandum of understanding with the province to bury the Eglinton line. That same deal with the province appeared to kill other light-rail lines that had been planned under Transit City and is expected to cost the city tens of millions in penalties.

But Joe Mihevc, the St. Paul’s councillor who solicited the legal opinion, said the mayor can simply not make that kind of decision on his own and erred in doing so.

“This legal opinion basically addresses whether the mayor had the authority to bind the city in those ways,” Mihevc told CBC News in a telephone interview on Sunday.

“And the legal opinion, which is very clear, says that we do not have a strong mayor system, the mayor does not have that executive power, and that he has to take it to Council for a vote.”

He said the mayor is obligated to bring his amended transit plan before City Council, which must approve it if it is to go forward.

Mihevc will unveil the legal opinion from lawyers Freya Kristjanson and Amanda Darrach on Monday. He intends to bring it forward for the city solicitor and city manager to examine.