Updated

A former chief executive of Sotheby's auction house testified that her boss and his counterpart at Christie's agreed behind closed doors that they "were killing each other on the bottom line, and that it was time to do something about it."

Diana Brooks told a jury Monday during the second week of the price-fixing trial of Sotheby's chairman A. Alfred Taubman that he ordered her to meet with her counterpart at Christie's and end the costly rivalry by eliminating discounts and by fixing commissions — a violation of antitrust laws.

He also warned her to keep quiet about it, she testified in federal court in Manhattan.

"I said, 'Fine, I wouldn't tell anyone,'" she said.

Brooks pleaded guilty in October 2000 to price-fixing charges. Hoping to avoid a three-year prison sentence, she also agreed to testify against Taubman.

Brooks, 51, the first woman to rise to chief executive at a major auction house, testified that when she told her boss last year it was time to come clean, he turned bitter.

Taubman allegedly warned Brooks, his trusted second-in-command, to not "act like a girl." Then he taunted her about possibly going to jail, she said.

Taubman, 76, of Bloomfield Hills, Mich., has denied charges he and Christie's chairman Anthony Tennant stole as much as $400 million in commissions from sellers from 1993 to 1999. Tennant, 71, of Andover, England, remains a fugitive.

Sotheby's pleaded guilty last year to price-fixing charges and was sentenced to pay $45 million.

Taubman's lawyer, Robert Fiske, has alleged that Christie's chief executive Christopher Davidge and Brooks cut a price-fixing deal without telling Taubman.

If convicted, Taubman would face up to three years in prison. The trial was to resume Tuesday.