Seiji Maehara, the new president of the Democratic Party, has suffered a setback in arguably his most important first task as head of the largest opposition force: Choosing his secretary-general — the second in command within the party leadership.

On Tuesday, Maehara announced he will appoint Atsushi Oshima, a 60-year-old Lower House member elected from Saitama Prefecture, as secretary-general.

But sources said that earlier, Maehara had unofficially decided to tap former prosecutor Shiori Yamao for the position.