In a pastoral letter to more than 50,000 Catholics in the diocese of St. Paul, Bishop Luc Bouchard wrote, "The integrity of creation in the Athabasca oil sands is clearly being sacrificed for economic gain."

The letter calls for a stop to oilsands development until adequate environmental protection measures are in place. He highlights the need for rules to lower greenhouse gas emissions and ambitious fuel-efficiency standards so oil is not wasted.

"The moral problem does not lie in government and industry's lack of a sincere desire to find a solution; the moral problem lies in their racing ahead and aggressively expanding the oil sands industry despite the fact that serious environmental problems remain unsolved after more than 40 years of on-going research," the letter says.