Japan's opposition leader, Banri Kaieda, quit Monday after his Democratic Party of Japan (DPJ) was defeated in general elections and he himself failed to secure a seat.
The DPJ gained 73 seats in the Sunday vote for the 475-seat lower house in parliament, 11 more compared to 2012, Xinhua reported.
Kaieda admitted the DPJ had failed to stop the runaway policy of Prime Minister Shinzo Abe.
During the election campaign, Kaieda criticized Abe's economic policy mix, or "Abenomics," for enlarging the country's wealth disparity.
Abe's Liberal Democratic Party and its junior Komeito partner took an overwhelming majority with 326 seats.
