The Champlain Bridge is Canada's busiest bridge. (Canadian Press)

Quebec is taking steps to prepare the ground for a new Champlain Bridge, despite the absence of any federal pledge to replace the aging span south of Montreal.

The last Conservative government promised $158-million  earlier this year to repair the decaying structure, but stopped short of committing to a complete overhaul of the decaying bridge.

Local politicians and business leaders announced Monday they are creating a Partnership Bureau to prepare for what they say is the inevitable decision to build a new bridge.

Quebec Transport Minister Sam Hamad said it's no longer a matter of "if" but "when" a new Champlain Bridge will be built.

The bureau will coordinate issues such as public transit and traffic congestion during any eventual bridge construction projects.

Quebec will also lobby for light rail passenger service to be built into any new bridge, he said.

A local coalition of mayors and industry leaders has lobbied hard for a new bridge, and say it's a leading campaign issue for voters on Montreal's South Shore.making the Champlain a federal election campaign issue.

During his visit to South Shore ridings last week, Liberal Leader Michael Ignatieff promised supporters that he would green-light a new  bridge if elected.

The Champlain Bridge is under federal jurisdiction, but all access routes fall under municipal and provincial watches.

Several reports suggest the bridge is decaying rapidly  and won't be able to handle regular traffic for much longer.

The Champlain Bridge is the busiest span in Canada.