Montreal's opposition parties are teaming up to fight a development project in Pierrefonds-Roxboro that is backed by Mayor Denis Coderre's administration.

They joined several hundred protesters who gathered on Monday evening outside City Hall to oppose the plan to build more than 5,000 homes in the L'Anse-à-l'Orme Nature Park.

​Environmental activists want to preserve the green space, which is located in western Pierrefonds and is home to a variety of wildlife.  

Now Vrai Changement pour Montreal and Projet Montreal say they will collaborate with each other to more effectively oppose the project.

They claim Coderre's administration has not been transparent about its plans for the green space. 

"It's not a fair process because it's not been a public process," Vrai Changement Leader Justine McIntryre said. 

"Nobody has had access to the full information. There has been no really public push for conservation until now, because nobody really knew what was going on in the file."

with files from Shaun Malley