A rookie Lower House member resigned Thursday from the Democratic Party of Japan to join a small group led by Nagoya Mayor Takashi Kawamura, weakening the ruling DPJ's power in the Lower House by yet another vote.

Yuko Sato's departure is another blow to Prime Minister Naoto Kan's attempts to hold his struggling party together. Sixteen members loyal to suspended DPJ kingpin Ichiro Ozawa recently attempted to form a new parliamentary group in the Diet, while Ozawa's close aide, Kenko Matsuki, resigned as parliamentary secretary of the farm ministry to protest Ozawa's suspension from the party.

Sato, first elected to the Lower House in the 2009 poll, once served as Kawamura's secretary. She will join Genzei Nihon (Tax Reduction Japan), established by Kawamura last April, but continue to represent the Nagoya No. 1 district in the lower chamber.