SOFIA, May 22 (Reuters) - Bulgaria's largest political party sought to annul the results of a May 12 election on Wednesday, threatening further uncertainty in the European Union's poorest country where street protests against austerity measures toppled the last government.
The centre-right GERB party, which was forced to resign by mass demonstrations in February, won 97 seats in the 240-strong parliament, but in its complaint it said its rivals campaigned illegally the day before the vote.
Legal experts said the complaint had little chance of success because GERB would have to demonstrate its support was definitely affected, and it was unclear how it could do that.
'GERB's request for cancellation of the election has no precedent in the European Union,' said Pascal Perrineau, head of the Paris-based Centre for Political Research. 'You just cannot urge people to vote again if you don't like the results.'
However, the weeks it may take the Constitutional Court to decide could deepen the political stalemate at a time when Bulgaria needs to draft a 2014 budget and negotiate EU funds to 2021 - key to reviving the economy and creating new jobs.
'We believe there are substantial violations on the day campaigning was banned and on election day too,' said GERB member Krasimir Tsipov after lodging a claim to annul the vote.
GERB said its support was dented by an announcement by state prosecutors on the eve of the poll that 350,000 illegal ballots were found at a printing shop owned by one of its councillors.
GERB leader Boiko Borisov denied any wrongdoing, but two rival parties held press conferences following the announcement even though political campaigning was banned. Borisov has said the incident knocked about 5-6 percent off the party's support.
He will get the first opportunity to form a government when he receives a mandate on Thursday, but his chances are seen as virtually zero.
If he fails, the second biggest party, the Socialists, will then seek enough support for a government made up of technical experts, headed by a non-partisan former finance minister.
The Socialists and their ethnic Turkish MRF allies are one seat short of a majority and will need to persuade individual MPs from GERB or the nationalist Attack party to offer them some kind of backing.
That would mean the government would be vulnerable to collapse at any time.
The process of forming a coalition will continue while the GERB complaint is pending, and Bulgaria could have a functioning government by the time the Constitutional Court rules - probably in one or two months' time.
Bulgaria will face new elections if the court cancels the May 12 results.
(Reporting by Tsvetelia Tsolova and Angel Krasimirov; editing by Mike Collett-White) Keywords: BULGARIA VOTE/
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