Thailand's opposition on Wednesday lost a legal bid to nullify a controversial election disrupted by anti-government protests, in a boost to Prime Minister Yingluck Shinawatra's crisis-hit administration.

The kingdom's Constitutional Court declined to consider the petition by the Democrat Party to annul the February 2 vote and disband Yingluck's party, saying there were insufficient grounds.

Yingluck called the polls in an attempt to assuage opposition protesters who have staged more than three months of mass street protests seeking her resignation.

The Democrats boycotted the vote, saying it would not end a political crisis stretching back to a military coup in 2006 that ousted Yingluck's elder brother Thaksin Shinawatra as premier.

The protesters want Yingluck to stand down to make way for an unelected "People's Council" to enact reforms to tackle corruption and alleged vote buying before new polls are held.

Demonstrators prevented 10,000 polling stations from opening in this month's vote, affecting several million people, mainly in opposition strongholds in Bangkok and the south.

The Democrats had argued that the failure to hold the entire election on the same day was an attempt to grab power unconstitutionally -- a complaint rejected by the court.

"This case is over," said the head of the opposition's legal team, Wiratana Kalayasiri, who filed the petition.

"But if the government does anything wrong again, we will make another complaint," he told AFP.

Yingluck's opponents say her government is controlled by her brother Thaksin, who fled Thailand in 2008 to avoid going to jail for a corruption conviction and now lives in Dubai.

Pro-Thaksin parties have won every election for more than a decade, most recently in 2011 under Yingluck, helped by strong support in the northern half of the kingdom.

The Election Commission has said the results of this month's election will not be announced until polls have been held in all constituencies.

Yingluck will remain in a caretaker role with limited power over policy until there is a quorum of 95 percent of the 500 seats in the lower house of parliament to enable the appointment of a new government.

The Election Commission on Tuesday set a date of April 27 for election re-runs in constituencies where voting was disrupted by protesters.

But there is still no decision on what to do about 28 constituencies that have no candidates because demonstrators blocked the registration process.

Protesters have occupied major intersections in the capital since January 13 in a self-styled "shutdown" of Bangkok, although disruption to people's daily lives has been limited.

Attendance has fallen sharply with most sites nearly deserted for much of the day and several thousand people joining the rallies in the evenings.

The protest leaders have called for a big two-day protest starting on Friday.

There has been a series of grenade attacks and shootings in the capital -- part of a wave of political violence linked to the protests that has left at least 10 people dead and hundreds injured.

Yingluck also faces an investigation by an anti-corruption panel into possible negligence of duty in connection with her flagship rice subsidy scheme -- a move that could potentially result in her impeachment.