The National Diet building stands in Tokyo, Japan, January 23, 2026. (Photo: VCG)

Japanese lawyers on Monday filed lawsuits at high courts across the country demanding the results of Sunday's House of Representatives election be nullified because it was unconstitutional as it was conducted without correcting vote weight disparities, local media reported.

The disparity between the most and least populated single-seat constituencies was 2.10-fold in the latest election, Kyodo News reported, citing its preliminary calculation.

As of Jan. 26, the day before official campaigning for the general election kicked off, the Hokkaido No. 3 district in northern Japan had the largest number of voters at 462,999, while the Tottori No. 1 district in western Japan had the smallest, with 220,820 voters, according to Kyodo News.

Lawyer Naofumi Ogawa told media that "equality in the weight of votes is an essential principle of the Constitution," calling for vote weight disparities to be rectified.

The lawsuits were instituted at courts, including the Akita branch of the Sendai High Court and the Osaka High Court. The Supreme Court is expected to issue a unified decision after those courts hand down rulings, possibly by March 2027, the report said.

The 2.10-fold gap compares with 2.06-fold in the previous lower house race in 2024, when it improved from 2.08-fold in 2021 after a revised law cut one seat each from 10 less-populated prefectures and allocated them to Tokyo and four other densely populated prefectures.