The 240-member Upper House voted Friday for its new president and vice president, but when ballots were cast for the latter, the tally came to 243.
The two positions were filled in the wake of the July 21 Upper House election, but in the initial voting for the vice president, three members apparently cast an extra ballot each, violating the Diet rule of one ballot per lawmaker.
The chamber annulled the outcome and held a second vote, which saw Azuma Koshiishi named to the post.
In the session, each Upper House member was given three ballot papers — one to choose the chamber's president, one for picking the vice president and one spare.
Later in the day two members — the Social Democratic Party's acting president, Seiji Mataichi, and independent Keiko Itokazu from Okinawa — admitted they each mistakenly cast their spare ballots along with their actual ballots. It's unclear who cast the remaining extra ballot.
Secretaries to Mataichi and Itokazu separately said the lawmakers were holding their spare ballots along with their actual ballots and put both of them into the ballot box together by mistake.
Chief Cabinet Secretary Yoshihide Suga was furious after hearing the news. He told reporters that said such an act goes against the very fundamental rule of the Diet.
"This is relevant to the foundation of parliamentary democracy," Suga said. "In the past a (similar) incident led to a lawmaker's resignation."
The ruling Liberal Democratic Party submitted a motion Friday evening to the upper chamber calling for the two lawmakers to face disciplinary action.
In April 2010, Masatoshi Wakabayashi of the LDP, which was an opposition party at the time, stepped down as an Upper House member to take the blame for pushing the voting button of an absent LDP colleague, Mikio Aoki, whose seat was next to Wakabayashi's.