TORONTO (Bloomberg) - Canadian stocks fell as a retreat in commodity and finance shares sent the main index to its longest monthly losing streak since 2001, after Canada's output shrank more than estimated and the US contracted the most since 1982.

Energy companies slid 1.4 percent on a drop in natural-gas prices and speculation producers' earnings will decline, after Petro-Canada reported a loss on Thursday. Manulife Financial Corp. declined, leading finance companies to a 7.1-percent drop in January after US regulators cut back the size of proposed relief for life insurers.

Research In Motion Ltd. rose, capping a 37 percent gain this month, on speculation it may win more clients than analysts forecast.

The Standard & Poor's/TSX Composite Index, which gets almost three quarters of its value from commodity and finance shares, fell 0.8 percent to 8,694.90 in Toronto. Canada's main stock benchmark slipped 3.3 percent in January for its fifth straight monthly decline, matching 2001's June-to-October retreat.

The S&P/TSX slid for seven consecutive months in 1984.

"Canada is widely seen as a flea on the back of an elephant," said John Stephenson, who helps oversee about $1.5 billion at First Asset Investment Management Inc. in Toronto.

"We're levered to global growth though our commodities. If there's any sign of growth we'll rally. If we don't have any, stocks will be poor. We'll trade sideways all year."

Canada's GDP shrank 0.7 percent in November, the most since 2003, and 0.3 percentage point faster than economists predicted. Output in the US, the nation's biggest trade partner, fell at a 3.8 percent annual pace in the fourth quarter.

Canada is the biggest supplier of oil and gas to US and sends more than 80 percent of all its exports to the neighbouring country.

Natural gas fell in New York, completing a 22-percent drop monthly drop as lay-offs and factory closures were forecast to reduce industrial demand for the fuel. Gas is down 68 percent from its July 2008 high. Petro-Canada fell 3.5 percent to C$26.59. The nation's third-biggest oil and gas producer posted a C$691 million ($565.8 million) fourth-quarter loss on Thursday, in part due to a 56 percent decline in oil prices during the period.