Snap elections loom in Bulgaria amid surging inflation and a diplomatic dispute with Russia after the centrist PP party of outgoing Prime Minister Kiril Petkov failed to muster enough support in parliament to form a new coalition.

Prime Minister-designate and PP co-leader Assen Vassilev said on Friday his party would not propose a new government because it had failed to win over four potentially supportive lawmakers needed for an absolute majority.

"We will return the mandate to form a government to the president unfulfilled. Unfortunately we did not succeed in finding 121 deputies to back our programme," Vassilev told a news briefing.

The PP-led government, which had pledged to tackle corruption and taken a strong stance against Russia's invasion of Ukraine, was toppled in a no-confidence vote last month after a coalition ally quit, stripping it of its majority.

There will now be two more attempts to form a government by other parties, but analysts doubt they will be successful and expect President Rumen Radev to appoint a caretaker government and to call fresh elections, which would be Bulgaria's fourth polls since 2021.

The prolonged political crisis is likely to imperil access to billions of euros in EU recovery funds and damage Bulgaria's prospects of joining the euro zone in 2024.

It may also impact Bulgaria's efforts to secure stable natural gas supplies after Moscow cut off gas deliveries to the country, which was almost completely reliant on Russian gas, over Sofia's refusal to pay in roubles.

Petkov, who has taken a strong pro-EU and NATO stance, has said a caretaker government may soften Bulgaria's rhetoric against Moscow's invasion of Ukraine and seek talks with Russia's Gazprom to restart gas deliveries.

Radev, the president, criticised a recent decision by Petkov's government to expel 70 Russian diplomatic staff warning of serious and long-lasting consequences for the Balkan country, which has close cultural and historical ties with Moscow.

A recent opinion poll showed that new elections were likely to produce another fragmented parliament, with the centre-right GERB party of former prime minister Boyko Borissov neck-and-neck with the PP party.

Speaking earlier on Friday, Petkov said that if new elections were held, they would be a test of whether Bulgarians want a normal democracy or to see what he called shady interests continue to siphon off public funds.

"It will almost be like a referendum pro or against the mafia," he said.