The Constitutional Court in Thailand has ruled that the general election in Februarty was invalid, deepening a political stalemate following weeks of opposition protests.
The election was called by Prime Minister Yingluck Shinawatra in an attempt to ease the country's political crisis.
But the court said the constitution had been violated because voting did not take place on the same day across the country, the BBC reports.
Polls were not held in a number of constituencies because protesters had blocked candidate registration.
The court, which ruled to void the election by six votes to three, was responding to a motion by a law lecturer who had challenged the election on a number of points. It is not clear when a new election will be held.
However, protest leader Suthep Thaugsuban, the deputy prime minister when the opposition were in power, said another election would face similar problems.
Thailand has been hit by anti-government protests since November 2013. The protesters, who are mainly urban and middle class, want Ms Yingluck's government replaced by an unelected "people's council".
They allege her brother, ousted leader Thaksin Shinawatra, controls her administration and say Shinawatra family money has corrupted Thai politics.
