Bank of Japan Gov. Toshihiko Fukui has made public that he invested 10 million yen in an investment fund led by maverick fund manager Mr. Yoshiaki Murakami, who was arrested June 5 on suspicion of insider trading involving purchases of Nippon Broadcasting System Inc. shares.

Although Mr. Fukui's investment was made while he was in the private sector, his failure to withdraw the investment when he became BOJ chief casts doubt on his neutrality as the nation's central banker and undermines the public's trust in him as the guardian of stability with regard to the value of the yen and overall price levels in the economy.

Mr. Fukui's revelation came Tuesday while he was answering a question from an opposition party member in the Upper House's Financial Affairs Committee. That day the Nikkei stock index plummeted over investor worries that the U.S. Federal Reserve may raise the federal funds rate again to fight inflationary pressures attributed to higher prices for oil and raw materials, and thus slow down the U.S. economy. A selling rush followed Mr. Fukui's statement. The 225-issue Nikkei stock average fell 614.41 points, or 4.14 percent -- the biggest single-day loss since Sept. 12, 2001, when it plunged 682.85 points following the 9/11 terrorist attacks in the United States.