The new Democratic Party's inaugural policy chief has been forced to apologize after it emerged that her office had claimed up to ¥4.29 million in fuel expenses in a single year.

Shiori Yamao, a female rights champion and rising star of the nation's new opposition force, said Wednesday that it was highly likely the "enormous gasoline expenses" for 2012 were the result of bookkeeping by a former secretary.

"I am very sorry for my failure to properly supervise" the secretary, Yamao, who was appointed as policy chief of the newly launched DP last month, told a packed news conference.