The Toronto Stock Exchange's S&P/TSX composite index <.GSPTSE> ended down 183.21 points, or 1.24 percent, at 14,595.11. It was the index's sharpest one-day loss since Sept. 13, with more than seven declining stocks for every advancer.

"It wasn't pretty," said Michael Sprung, president at Sprung Investment Management. "Oil's been having a very tough week, and the stocks are reflecting that."

The index's large energy group fell 1.7 percent as oil prices dropped for a fourth day, down 3 percent after a record weekly build in U.S. crude inventories stoked concerns about a global supply glut. [O/R]

The most influential weights on the Canadian index included some major pipeline companies. TransCanada Corp (>> TransCanada Corporation) fell 4.6 percent to C$57.82 and Enbridge Inc (>> Enbridge Inc) declined 2.6 percent to C$55.96.

TransCanada said it would sell its U.S. Northeast Power business and do a bought deal common share offering to fund its acquisition of the Columbia Pipeline Group earlier this year.

All 10 of the index's groups fell, with the heavyweight financials sector down 0.8 percent, and the materials group, which includes precious and base metals miners and fertilizer companies, giving up early gains to end 1.8 percent lower.

Sprung said a range of factors including dismal earnings and uncertainty over the outcome of the Nov. 8 U.S. election likely contributed to muted investor appetite.

Aecon Group Inc (>> Aecon Group Inc) fell 16 percent to C$14.38 after the construction company's profit missed expectations and revenue fell.

Detour Gold Corp (>> Detour Gold Corporation) slumped 18.8 percent to C$21.23 after issuing lackluster production guidance.

Valeant Pharmaceuticals International Inc (>> Valeant Pharmaceuticals Intl Inc) fell 9.1 percent to C$28.34. The drugmaker is being sued on behalf of former investors in Sprout Pharmaceuticals Inc, which Valeant bought last year for $1 billion, over its alleged failure to successfully market the female libido pill Addyi.

Canadian uranium producer Cameco Corp (>> Cameco Corporation) reported a better-than-expected quarterly profit, largely helped by a jump in uranium sales volumes. Its shares jumped 12.1 percent to C$11.15.

(Additional reporting by Fergal Smith; Editing by Jonathan Oatis and Richard Chang)

By Alastair Sharp