Bulgarian Prime Minister Boyko Borisov has said he is "utterly disappointed" by a voting in Parliament in which MPs rejected two of the three questions to be put forward in a referendum on election rules.

Lawmakers on Tuesday voted against most of the proposals of President Rosen Plevneliev, who demanded that citizens should have their say on the introduction of majority elements in the electoral system, compulsory voting, and remote electronic voting.

Only a question regarding electronic voting will be part of the referendum that is most likely to be held this autumn along with local elections.

Borisov told reporters he personally had fully supported the idea that all three questions should be put to a vote.

He blamed "partners" in the government for the failure of President Plevneliev's initiative, in an apparent reference to the right-wing Reformist Bloc, the junior partner in a coalition cabinet dominated by Borisov's center-right GERB party.

"We backed the President as much as we could on the referendum, out partners, regrettably, didn't... Our colleagues from the Reformist Bloc should learn that it is good for them to say in public they are real democrats, but their job in Parliament is to remain on their seats. When planning their trips, they should know that in the last weeks the most important issues are decided upon and they should be in the [plenary] hall," the website Dnevnik.bg quotes him as saying.

The Reformist Bloc had been among the staunchest supporters of all referendum questions, but backtracked on majority voting.

Borisov, however, warned against suggestions by some political parties that a referendum only concerning the issue of electronic voting should not take place.