Jan. 22 (Bloomberg) -- Brazil's main stock index plunged after the central bank last night unexpectedly kept its benchmark interest rate unchanged. Brasil Telecom SA, the operating unit of the country's third-largest phone company, led the decline.

The Bovespa index of the most-traded stocks on the Sao Paulo Stock Exchange fell 573.68, or 2.5 percent, to 22,728.14 at 8:11 a.m. New York time, heading for its biggest tumble since declining 3 percent on Oct. 23.

The central bank yesterday decided to maintain its benchmark lending rate at 16.5 percent, while a median estimate with 33 economists surveyed by Bloomberg was predicting a 0.5 percentage- point cut.

Last Updated: January 22, 2004 08:13 EST