The Washington environmental-activist group said BP's $3.1 billion deal with Calgary, Alberta's Husky Energy Inc. (OTCPK:HUSKF) to extract crude oil from tar sands amounted to the "biggest global warming crime" in history.

Tar sands -- a heavy mixture of bitumen, water, sand and clay -- lay beneath more than 54,000 square miles of northern Alberta forest.

BP and Husky said the planned facility will able to produce 200,000 barrels of crude a day by 2020.

Producing heavy tar-sand oil generates up to four times more carbon dioxide, the principal global-warming gas, than conventional drilling, The Independent reported.

In contrast to conventional crude-oil drilling, tar sand deposits must be strip-mined or made to flow into producing wells using steam or solvents to reduce the heavy oil's thickness.

These processes use a great deal of water and require large amounts of energy.

A BP spokesman told the British newspaper it planned to use an extraction method that was environmentally sensitive, but would still increase its carbon footprint.

"These are resources that would have been developed anyway,"the spokesman said.