Ten corporate customers were involved in Yamaichi Securities Co.'s dubious "tobashi" dealings to hide losses that eventually led to the collapse of the brokerage, Tsugio Yukihira, chairman of the failed firm until last August, said Tuesday in unsworn testimony in the Diet.

Yukihira said that Big Four brokerage Yamaichi racked up more than 200 billion yen in losses off its balance sheet by shouldering the debts incurred by the 10 customers. He said he was unable to recall any of the names of the client firms. The firms entrusted the brokerage with specified amounts of money to invest as it saw fit. The sharp fall of stock prices in the early 1990s and bad dealings by Yamaichi generated the losses, the 66-year-old Yukihira said.

"Traditionally, corporations made up the great majority of customers of our 100-year-old firm," Yukihira told the Lower House Budget Committee. "Therefore, we believed that Yamaichi would not be able to survive if our firm caused huge losses for our corporate customers. "We kept (the debts) off our balance sheet because we feared that making such huge debts public would force Yamaichi to fall out of the Big Four group," he said.