The Supreme Court dismissed appeals Tuesday filed by lawyers seeking to invalidate the results in several constituencies in the November 2003 House of Representatives election.
The lawyers claimed the seat distribution did not reflect population density.
Presiding Justice Toyozo Ueda of the Third Petty Bench said the lawsuits had lost their merit due to Prime Minister Junichiro Koizumi's dissolution of the Lower House on Aug. 8 and the subsequent Sept. 11 election.
The Tokyo High Court rejected the petitions in December 2004, saying the Diet had discretion in ensuring fairness in the allocating of seats.
The high court, however, acknowledged that disparity in the weight of the vote widened sharply to 2.064, which means a lawmaker from the most populous constituency was representing more than twice as many voters as one in the least populous district.
The appeals concern the Nov. 9, 2003, election for six single-seat constituencies in Tokyo, one in Kanagawa and two in Chiba Prefecture.
Eight of them were moved to the Supreme Court's Grand Bench, where all 15 justices were to examine the cases in July. But they were moved back to the Third Petty Bench after the Lower House was dissolved in August.
The Supreme Court dismissed an appeal concerning the remaining case, in the Tokyo No. 4 constituency, in July, after Liberal Democratic Party lawmaker Kazuyoshi Nakanishi, who represented the constituency, resigned in March over his arrest on allegations of groping a woman in Tokyo.