A referendum in Bulgaria on whether to build a second nuclear power plant has failed due to insufficient turnout, official results showed Tuesday.

Only 1.4 million people, or just over 20 percent of the electorate, voted in Sunday's poll, far short of the 60 percent needed for the plebiscite to be valid, electoral officials said.

In the Balkan state's first referendum since the end of communism, three in five voters backed the revival of an off-again, on-again project for a second 2,000-megawatt nuclear power plant at Belene, northern Bulgaria.

Bulgaria's right-wing government ditched the project last March due to financial constraints, an inability to find a Western investor and constant price-haggling with Atomstroyexport, the Russian company that would build the plant.

The turnout was just enough to require parliament to review the issue within the next three months, although lawmakers will not be obliged to revive the deal.