Former Prime Minister Yukio Hatoyama said Monday that he will leave the opposition Democratic Party of Japan, which he helped establish.
Hatoyama, 66, did not run in last December's general election, saying the DPJ had lost its way under Prime Minister Yoshihiko Noda and was no longer the same party he founded.
On Monday, Hatoyama informed his constituency in Hokkaido of his decision, Sankei Shimbun reported.
Hatoyama became prime minister in 2009 when the DPJ ended half a century of almost unbroken rule by the conservative Liberal Democratic Party. He was initially seen as the bringer of change, but his reputation took a battering when he reversed course on a plan to remove a controversial U.S. air base in Okinawa.
Having angered voters and provoked Washington in a short space of time, he resigned from the post after just nine months in office, short even by the standards of Japan's revolving-door premiership.
Last year, Hatoyama opposed Noda's sales tax hike proposal, as well as plans to have Japan join the Trans-Pacific Partnership free trade talks.
He is a fourth-generation politician and the second in the family to become prime minister, after his grandfather. His other grandfather founded tiremaker Bridgestone.© Japan Today/Reuters