The three-point referendum on the voting system of Bulgaria cannot be binding as nearly all vote protocols have been counted, official data reveals after a day of ambiguous messages.

Turnout is expected to fall short of just over 3.5 million votes - the figure from the previous parliamentary election.

With just below 100% of the vote counted, the current activity figure is just 13 000 votes below this threshold, the Central Election Commission (CEC) says.

CEC spokersperson Tsvetozar Tomov, speaking for private bTV station on Tuesday, urged patience as final results were yet to be confirmed by the election authorities.

But its most recent data refutes earlier reports of big enough activity which emerged as activity was nearing the threshold.

The calculations made by Novinite and national Bulgarian media had not taken into account the large number of void ballots, which with nearly all protocols processed is above 83 000. 

Regardless of the definitive outcome, the activity which surpasses 20% of eligible voters obligates Parliament to debate and vote on the questions.