Cities that draw their water from the Great Lakes have aligned to oppose a decision that allows Waukesha, Wisconsin to divert water from Lake Michigan to its community.

In June, the Compact Council - the group which oversees details of how neighbouring American states manage use of the Great Lakes - allowed Waukesha, a suburb of Milwaukee, to draw water from Lake Michigan, even though the city has access to the Mississippi River watershed.

Waukesha made the application when the level of radium in its aquifers exceeded American federal regulations.

The Great Lakes and St. Lawrence Cities Initiative, an international group representing Thunder Bay, Niagara Falls, Montreal and Toronto among others, requested a hearing to challenge the decision made by the council.

Mayor Denis Coderre of Montreal, who chairs the Cities Initiative, said "for the Compact Council to grant an exception to the first application that does not meet the conditions of the Compact sets a very bad precedent."

"To make sure the Compact and Great Lakes are not compromised in the future, this decision should be overturned," he said.

"We are taking this step to launch a legal challenge to the Compact Council's decision regarding the Waukesha water taking application because we do not feel that Waukesha met the rigorous standard set in the Compact to qualify for an exception to the ban on water diversions to communities outside of the basin," said Mayor Sandra Cooper of Collingwood, Ont., who is also the treasurer for the Inititative.

The challenge was issued to the Compact Council Monday.