Bulgaria's opposition Socialists filed a no-confidence motion against the centre-right government Friday over its decision to drop a deal with Russia for a new nuclear plant on the Danube.

The motion, which was also backed by lawmakers from the ultra-nationalist Ataka party, is the fourth against the government of Prime Minister Boyko Borisov.

However it stands little chance of success as the minority cabinet enjoys support from enough right-wing opposition deputies to overthrow it.

Bulgaria announced last week a decision to abandon a project for a new 2,000-megawatt nuclear power plant at Belene on the Danube to be built by Russian company Atomstroyexport.

Borisov justified the move by saying the government could not find a foreign investor to join the deal after the withdrawal in 2009 of German utility RWE.

The government was also unable to pay by itself the estimated price of about six billion euros ($8 billion) plus interest on eventual credits it would have to take to fund the project, he added.

Price-haggling with the Russian company and doubts about the project's economic feasibility had already dogged the deal, which was also opposed by local environmentalists and Bulgaria's Western partners as strengthening Russia's grip on the Balkan country.

Bulgaria is almost totally dependent on Russia for its gas and oil supplies. Its only existing nuclear power plant at Kozloduy, also on the Danube, is also Russia-built and running on Russian fuel.

But the Socialists charged on Friday that the decision to drop Belene was "fatal" for the development of Bulgaria's nuclear energy sector and would cause Bulgarians to buy much more expensive electricity in the future.

The motion is expected to be put to a vote in parliament next week.