Mayor Valérie Plante has vowed to send the promoters of a sprawling new development under construction at the former Montreal Children's Hospital back to the drawing board for failing to include the promised social housing units in their plans.

"Enough," Plante told reporters Monday. "The promoter was well aware of the social agreement connected to this project and it was absolutely necessary to have some social housing."

The agreement to build 180 social housing units, made two years ago, was a condition for the city's acceptance of the project.

Speaking on the CBC Montreal's Daybreak Tuesday, Plante admitted the agreement, which she calls a social contract, "doesn't have much teeth."

In July, Plante said negotiations between the developers and the city were going poorly and that the social housing aspect of the project was in danger.

Now, she said developer Philip Kerub of High-Rise Montreal has nixed social housing altogether, opting for the project to be entirely made up luxury condos instead.

The mayor says the city is responding by blocking a sixth tower that was to be built.

"Today, we will be voting to go back to the original version — which is: you can build, but it will be a four-storey building. That's it," Plante said.

'Dire' social housing situation, advocate says

She says that's why her administration adopted a bylaw in June to require developers of projects with more than 49 units to include social housing equal to 20 per cent of the building's livable space.

"[It's] exactly to avoid that kind of situation," Plante said.

Corey Gulkin, a spokesperson for the Peter-McGill Community Council, said the social housing portion of the development was crucial for the neighbourhood.

"The situation in Peter-McGill is fairly dire," Gulkin said, also speaking on Daybreak. "Rents are extremely high downtown and there's been an influx of development, and there has not been the social and affordable housing to match."

Last year, Devimco, one of the project's developers, said it couldn't build an elementary school on the site because it couldn't wait any longer for the provincial government and school board to provide plans.

"We're slowly kind of watching the developer weasel their way out of building these public spaces," Gulkin said.

She said the plans now show less green space than originally planned, but that the promoters appear to still be going ahead with a cultural centre.

Gulkin says she's happy with the new bylaw, though it has no binding power on the Children's development because it was approved before the regulation went into effect.

She said the problem dates back to when former mayor Denis Coderre's administration sold the site without any building conditions.

High-Rise Montreal denied a request for an interview by Daybreak.