BANGKOK – Thailand's Constitutional Court ruled February's election invalid in a further obstacle to Prime Minister Yingluck Shinawatra's efforts to form a new government.

The judges voted six to three Friday that the Feb. 2 poll, which was boycotted by the main opposition party and disrupted by protesters, was unconstitutional because voting could not take place in 28 of 375 constituencies on that day.

"Holding an election for the 28 constituencies after February 2 cannot be done," the court said in a statement.

The ruling leaves the Ying­luck administration stuck in a caretaker role with limited powers. Yingluck called fresh elections in December in a bid to defuse street protests aimed at replacing her government with an unelected council.

The opposition Democrat Party refused to take part in the poll while the protesters, led by former Democrat power broker Suthep Thaugsuban, blocked candidates from registering in some areas. That left the election incomplete and Yingluck's government and the Election Commission at odds about how to proceed.

A new vote may take at least three months to organize, said Suphachai Somcharoen, the commission's president.

Verapat Pariyawong, an independent political analyst, said there were solutions provided in the constitution to resolve such disruptions.

"The court is paving ways for anyone to have the power to nullify an entire election simply by obstructing candidates from registering in a single district," he said.

The past five elections have been won by parties allied with Yingluck's brother, former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 coup. The Democrats have not won a national election in more than two decades.