Local election boards in Okayama and Shimane prefectures appealed lower court rulings Monday that said December's general election was unconstitutional and invalid because of the significant disparity in vote weights.
The Okayama prefectural election board, in protesting the March 26 decision by the Hiroshima High Court's Okayama branch, urged the Supreme Court to make a final judgment about the vote disparity.
The board contended that the decision determined the electoral zoning rules unconstitutional as a whole, thus bearing "a big impact on election credibility."
The Shimane prefectural election board followed suit later in the day and appealed the March 26 decision by the Hiroshima High Court's Matsue branch to the top court.
Late last month, the Okayama branch decided to void the House of Representatives election outcome in Okayama's No. 2 constituency.
The branch did not say when its decision would take effect, meaning that if the ruling becomes final, there must be a new election.
The Matsue branch decision also called the poll unconstitutional but didn't nullify it.
In a separate but related case, the Hiroshima prefectural election board has appealed a Hiroshima High Court ruling on March 25 nullifying the election results in the Hiroshima No. 1 and 2 districts.
The high court said that the election results would not be invalidated until Nov. 26, the date a Lower House council began work on revising single-seat electoral districts a year ago.
The Diet enacted a law last November to reduce vote weight disparities by cutting the number of single-seat constituencies in the Lower House to 295 from 300, but the December election was conducted with the same number as in the 2009 contest.
The courts have slammed lawmakers for being too slow to rectify the disparity, although they have long been hesitant to give clear-cut rulings to declare a Lower House election unconstitutional or invalid.