Tokyo Stock Exchange Chairman Taizo Nishimuro will double as president after the current president, Takuo Tsurushima, quits to take responsibility for the failure of the bourse's computer system to prevent a costly erroneous stock order earlier this month, according to industry sources.

Since Tsurushima, 67, suggested Dec. 11 he would step down over the debacle, Nishimuro, 69, tried but was unable to find a successor from within the industry, the sources said.

Nishimuro will double as president until the TSE shareholders' meeting in June, the sources said. Senior Managing Director Sadao Yoshino, 61, with executive rights, also will be stepping down.

The changes will be formalized Tuesday at a meeting of directors, the sources said.

Mizuho Securities Co. erroneously placed a sell order at an unrealistic price, and when the TSE's system did not prevent it the brokerage took a hit estimated at more than 40 billion yen.