Social Democratic Party leader Tadatomo Yoshida said Thursday he will step down as head of the small opposition party to take the blame for its poor showing in Sunday's Upper House election.
"I'm keenly aware of the responsibility (for the election showing) as the party leader," 60-year-old Yoshida said at an executive board meeting.
The board agreed to select a new leader before holding a conference of representatives of nationwide branches in early September.
The party had aimed to secure two seats — one for Yoshida and the other for former party leader Mizuho Fukushima — in the House of Councilors election but only Fukushima was able to retain her seat.
Party members also confirmed at the meeting they are in the final stage of negotiations with the People's Life Party, another small opposition party, to form a joint parliamentary group in both the Lower and Upper houses, starting from the next extraordinary Diet session.
The session is scheduled to be convened Aug. 1 to elect the Upper House president and vice president.
Yoshida, who was elected as an Upper House member for the first time in 2010, succeeded Fukushima as party leader in 2013 and was re-elected to the post by default last December.