Seiji Maehara has resigned as leader of the Democratic Party to take responsibility for the disarray following a failed merger with the fledgling force led by Tokyo Gov. Yuriko Koike.
Maehara said Monday he will leave the Democratic Party and join Koike's Kibo no To (Party of Hope) . He has already been included in the list of its parliament group, according to the Lower House secretariat.
The party accepted Maehara's resignation and will pick a new leader Tuesday ahead of the special Diet session starting Wenesday.
"It is natural to take responsibility for the failure (in the election) as politics is all about results," Maehara told reporters in the party's headquarters. He had assumed the top post in early September.
The party now comprises 46 members of the Upper House and 18 lawmakers who ran as independents in the Oct. 22 Lower House election, along with its regional chapters.
Among them, 13 Lower House lawmakers, including former DP President Katsuya Okada, have recently formed an independent group in the Diet.
The 55-year-old Maehara had effectively disbanded the DP and sought to have all of its Lower House members run as part of Kibo no To in an attempt to topple the ruling coalition led by Prime Minister Shinzo Abe's Liberal Democratic Party.
Kibo no To absorbed many DP lawmakers, but in doing so disappointed voters as Koike said she would "exclude" left-leaning members of the DP whose views on such fields as national security and revising the pacifist Constitution were different from hers.
Kibo no To fielded 235 candidates nationwide in the 465-seat Lower House election but secured only 50 seats. The LDP won 284 seats, maintaining a two-thirds majority along with its coalition partner, Komeito.