Japanese courts are stepping up pressure on the government to reform the country's electoral system or risk having the results of last year's general election invalidated.
Six regional high courts are to deliver rulings on Tuesday in so-called "one person, one vote" cases brought by constitutional activists. The Japanese electoral system gives voters in sparsely populated rural districts disproportionate power.
The courts could follow the lead of the Hiroshima high court, which on Monday became the first Japanese court to declare outright that the results of a parliamentary election should be discarded.
No politician will be forced to give up a parliamentary seat immediately as a result of the Hiroshima ruling, nor will the overall election result – a victory for Prime Minister Shinzo Abe and his Liberal Democratic Party – be nullified.
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The Hiroshima court said its ruling, which applies to two local electoral districts, would not take effect for seven months, giving the government time to appeal to the Supreme Court, move forward with planned electoral reforms, or both.
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"I will examine the details of the ruling and respond appropriately," Mr Abe said.
Japanese courts, including the Supreme Court, have previously ruled that the country's voting-system disparities violated the constitution. However, they have stopped short of invalidating election results, preferring instead to give parliament a chance to rectify the system.
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But politicians have been deadlocked over proposals to reduce the number of seats from rural areas. Mr Abe's party is seen as especially reluctant to address the issue, since it has traditionally enjoyed strong support in the countryside.
In the December 2012 general election, the surplus of seats in the countryside meant that the ballot cast by each voter in the most over-represented rural district was worth 2.43 votes in the most crowded district in Tokyo.
"The distortion caused by this disparity is so heavy that it can no longer be tolerated under the constitution," the Hiroshima court ruled.