TORONTO (Reuters) - The Toronto Stock Exchange's main index kicked-off the week with a sharp across-the-board decline yesterday as commodity prices fell and prospect of more bank writedowns rose.

All of the TSX's 10 main sectors were lower, with materials shares leading the way, shedding a total of four percent, hit by a gold-price drop as the dollar steadied against the euro.

Financial shares fell 0.8 percent after National Bank of Canada said that it expects to take a pretax charge of C$575 million ($587 million) on its holdings in non-bank asset-backed commercial paper.

The sector was also hurt by a brokerage downgrade of US bank Citigroup , which prompted worries that the bank fallout from the credit crisis might not be over.

The S&P/TSX composite index closed down 182.12 points, or 1.35 percent, at 13,348.24. The market has tumbled 8.7 percent since the beginning of November.

National Bank was the latest of several Canadian institutes to reveal write-offs due to problems in the US sub-prime market.

Shares in National Bank finished higher, however, up 77 Canadian cents, or 1.5 percent, at C$51.80.

Elsewhere in the sector, Royal Bank of Canada was down C$1.08, or 2.1 percent, at C$50.06.

In the materials group, home to resource shares, Barrick Gold was down C$1.57, or 3.9 percent, at C$38.27, and Goldcorp slipped C$1.19, or 3.8 percent, to C$30.13.

The lightweight consumer staples group slid 2.3 percent, with Loblaw giving up C$2.10, or 6.1 percent, to close at C$32.44 after the company reported disappointing results last week.