The man who was the Ministry of Economy, Trade and Industry's top official when the Fukushima disaster unfolded said he regretted underestimating the tsunami danger when METI was reviewing earthquake-resistance guidelines for nuclear plants before the crisis.

"We should have used our imagination," said Kazuo Matsunaga, who was vice minister of economy, trade and industry when the meltdowns began in March last year, told a Diet-appointed panel probing the disaster Wednesday.

He was also involved in revising the guidelines as chief of the Nuclear and Industrial Safety Agency, which METI oversees, between 2004 and 2005.