Bulgaria will hold a snap parliamentary election on July 11, after a third and final attempt to form a government following April 4 polls that led to a fragmented parliament failed, President Rumen Radev said on Wednesday.

Long-serving Prime Minister Boyko Borissov's centre-right GERB again emerged as the largest party after last month's election but it lost seats amid widespread public anger over entrenched corruption in the political elite.

With Borissov short of a majority and unable to forge a new coalition, the president had asked a new anti-elite party led by TV host Slavi Trifonov to do so but it also failed, as did the third largest party in the new parliament, the Socialists.

"Bulgaria needs a strong-willed political alternative, which the current parliament failed to produce," Radev said after the Socialist Party returned the mandate to form a government.

The stalemate left Radev, a harsh critic of Borissov's failure to crack down on graft, with no alternative but to appoint an interim technocrat administration and call another snap election.

"Next week I will dissolve the parliament and appoint an interim government. In this situation, the election is expected to be held on July 11," Radev said in a live broadcast.

Radev said he plans to appoint experts as interim ministers. They will face a challenging agenda of managing the coronavirus pandemic and its economic impact and of ensuring a fair election in the European Union's poorest member state.

A recent opinion poll showed Borissov's GERB remains the most popular party, but its key rival, Trifonov's There Is Such a People, is a close second, raising the prospect of continued fragmentation in which the politicians will struggle to form a stable coalition government.

Radev, a largely ceremonial head of state with limited powers under Bulgaria's post-communist constitution, appealed to the parties to find common ground and to avoid prolonged deadlock.