Bulgaria's government was spared a motion of no-confidence over its decision to drop a deal for a new nuclear plant on the Danube after the parliament speaker ruled Thursday the vote no longer had sufficient backing.

"There are no constitutional grounds for such a vote after eight lawmakers who had demanded the motion withdrew their signatures," Parliament Speaker Tsetska Tsacheva said.

The motion was floated by the opposition Socialists, who control 40 seats in parliament.

They had received backing from eight MPs from the nationalist Ataka party, taking support for the motion to the required level of 48, but the eight withdrew their signatures on Thursday.

The centre-right government holds a large majority in parliament and would have easily fought off the vote.

Bulgaria announced last month 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.

Prime Minister Boyko 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.

European Union member Bulgaria is almost totally dependent on Russia for its gas and oil supplies.