A Romanian court has rejected an appeal by the ruling party's leader to quash his sentence for vote rigging during a 2012 referendum, striking a blow to his ambition to become prime minister.

The High Court for Cassation and Justice on Monday rejected an appeal by Liviu Dragnea, who heads the Social Democratic Party, to overturn a two-year suspended prison sentence he received in April 2016 for inflating voter numbers in a referendum to impeach ex-President Traian Basescu. The ruling is final.

The conviction means Dragnea can't become prime minister, something he calls unfair. In February, he launched a legal bid to get it overturned.

The Social Democrats won the December parliamentary election, and Dragnea was expected to be appointed prime minister.

The referendum failed because turnout was too low.