No winner has yet been declared in the parliamentary election, which was boycotted by the opposition Democratic Party. The court ruled 6-3 that the results are not valid because the voting was not completed in a single day, the Bangkok Post reported.
The governing Pheu Thai party accused the court of acting illegally, the Post said. It blamed the opposition for problems in 28 of the 375 parliamentary districts.
The court's ruling effectively rewards those who break the law and obstruct voting, the ruling party said. Any new election could be voided using the same tactics.
Prime Minister Yingluck Shinawatra, sister of the ousted former prime minister, Thaksin Shinawatra, remains head of government.
Pheu Thai said the court has a conflict of interest because it was created by the leaders of the coup that forced Thaksin out of office and into exile.
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