Bulgaria's new Prime Minister has pledged to expose all corruption.

Kiril Petkov was finally voted into office on Monday when lawmakers  approved the lineup of his broad coalition government, ending months of political deadlock in the European Union's poorest member state.

Petkov, 41, is a Harvard-educated entrepreneur whose new centrist faction We Continue The Change (PP) won Bulgaria's third national election this year in November, securing a clear majority of 134 votes in the 240-member parliament.

He will lead an unprecedented ruling coalition with the leftist Socialists, anti-establishment ITN party and the centre-right Democratic Bulgaria, united under the motto "zero tolerance to corruption", for a four-year term.

"I will insist that corruption from the lowest to the highest level be exposed," Petkov told the chamber prior to his election, appealing to all lawmakers to support legal changes needed to overhaul the judiciary.

The new government takes over following eight months of political impasse and two interim administrations after anger against high-level graft ended the decade-long rule of former centre-right premier Boyko Borissov.

Wearing a black face mask, Petkov shook hands with his closest allies as he received a standing ovation from the ruling coalition's lawmakers upon his election.

Petkov will navigate a four-party alliance of Borissov's political opponents with a promise to clean up public life, speed up growth to over 5% a year and facilitate a faster catch-up with richer Western peers.

His Cabinet will have to steer Bulgaria through challenges ranging from tackling high energy costs and low vaccination rates against coronavirus to preparing the small and open economy for euro zone entry in 2024.

Petkov pledged to deepen Bulgaria's integration into the EU and transatlantic NATO alliance and intensify talks with neighbouring North Macedonia to solve a historic dispute that has prompted Sofia to block the start of EU accession talks with Skopje.