Canada's dollar had the worst one-day fall on record today and dropped below 81 cents US as a result of lower commodity prices, plunging stock markets and uncertainty about the economy.

The loonie began the North American trading day down but took a big dive as U.S. Treasury Secretary Henry Paulson announced changes to the US$700-billion rescue plan for troubled financial firms.

The currency kept falling as the day wore on, dropping by as much as 2.84 cents in late afternoon. It closed at 80.81, down 2.77 cents US.

That's the biggest one-day drop on record at the Bank of Canada and surpassed the 2.69-cent fall on Oct. 10, when the currency spent much of the day down more than three cents before rallying.