Montreal health officials demanded a legal exemption Wednesday to allow four "shooting galleries" for addicts to inject drugs legally and under supervision.

The project would create three consumption rooms open in downtown Montreal and a mobile unit to service the city's farther reaches, city health chief Richard Masse told AFP.

Running the four centers will cost about Can$2.7 million ($2.5 million) annually.

If the city's agency is given the green light for exemption from Canada's Controlled Drugs and Substances Act, the shooting galleries could open their doors in spring 2014.

"We hope the Canadian government will grant us an exemption from the act as soon as possible," said Masse.

Two consumption centers already exist in the western city of Vancouver. In 2011, the Supreme Court dismissed a Health Ministry attempt to have them closed, upholding the centers' exemption from the drug law.

Consumption rooms, known in Canada as "supervised injection sites," allow users to inject drugs in a safe and hygienic environment where medical personnel are available and addicts are shielded from police arrest.

Europe's first consumption room opened its doors in Switzerland in 1986. Around 100 exist today, notably in Denmark, Germany, Luxembourg, the Netherlands, Norway and Spain.