LDP, JIP and DPP submit Lower House seat-cut bill, driving contentious reform

The ruling Liberal Democratic Party, its coalition partner the Japan Innovation Party (JIP) and the opposition Democratic Party for the People (DPP) jointly submitted a bill Thursday to cut 31 Lower House seats, advancing a contentious electoral overhaul.

All cuts would come from proportional representation seats, leaving the number of single-member districts unchanged. The three parties aim to pass the bill by Dec. 12, when the current Diet session is scheduled to end.

“I hope the three parties will work together to secure the bill’s passage,” said Katsunobu Kato, senior lawmaker and head of the LDP’s task force for political system reform, during a meeting with his counterparts Thursday morning.

The LDP and the JIP, also known as Nippon Ishin no Kai, submitted a similar bill in June that would have cut 45 proportional seats — roughly 10% of the chamber’s total — if broader electoral reform legislation failed to pass within a year of the law’s promulgation.

The Liberal Democratic Party's Katsunobu Kato (center) and his counterparts hold the seat cut bill in Tokyo on Thursday. | JIJI

Facing opposition resistance, however, the LDP proposed a smaller reduction, citing a projected 6.7% decline in Japan’s population between 2015 and 2030. The three parties formally signed the agreement last month.

The revised bill would also merge the Chugoku and Shikoku proportional representation blocs, reducing the total number of blocs nationwide from 11 to 10.

Proportional seats would be allocated using a modified Sainte-Lague system, which is intended to give smaller parties a better chance of winning seats than the current D’Hondt method.

At the same time, candidates who run in both tiers and lose in their single-member districts would need at least one-sixth of the valid votes cast in their district to qualify for a proportional seat, in a change from the current one-tenth threshold.

Komeito, the largest party in the Lower House’s main opposition bloc, has argued that cutting only proportional representation seats would give greater weight to single-member districts. The Japanese Communist Party has also voiced its opposition, saying the package would make it harder for smaller parties to win seats and weaken their representation.

The proposed legislation will also leave proportional representation seats vacant if a party lacks enough candidates to fill them, rather than reallocating them to other parties as is done under the current system.

If enacted, the changes would take effect alongside a separate law redrawing single-member district boundaries based on the 2025 census, potentially in 2027. The LDP, JIP and DPP together hold majorities in both chambers, strengthening the bill’s prospects of passage.

The LDP has proposed starting deliberations by the Lower House special committee next week, but the parties have yet to agree on a timetable.