Economy minister Hiroshige Seko said Tuesday he will voluntarily return a month's pay after his ministry offered annual remuneration of over ¥100 million to executives at a government-backed investment fund and later retracted it for being "too high."

"We have caused an administrative blunder where we proposed an undetermined plan to the management of the (Japan Investment Corp.) and canceled it, triggering mutual distrust" between the ministry and the fund, Seko told a news conference.

Takashi Shimada, vice minister at the Ministry of Economy, Trade and Industry, will voluntarily return 30 percent of a month's wages to take responsibility for insufficient supervision as the ministry's top bureaucrat.