Virant said he concluded that the motion for the bad bank referendum did not meet legal requirements after it was found that the proponents used simply copied signatures from the motion for the referendum on the sovereign holding bill.

The speaker had indicated as such already on Wednesday, a day after the opposition Positive Slovenia, helped by an MP of the fellow opposition SocDems and two independent MPs, filed the referenda motions.

Virant said at the time he would take extra time to consult with the parliamentary legal service and experts before making a decision. A number of legal experts have since publicly said that a motion endorsed by scanned signatures is invalid.

Responding to the doubts about the motion, PS leader Zoran Janković said earlier on Friday that if Virant cared at all "about democratic decision-making in this country" he would allow the referenda motions to stand since the MPs involved confirmed their intent to support both motions.

Virant announced that the National Assembly would convene an emergency session on Tuesday to discuss the motion for the sovereign holding referendum if the government does not first petition the Constitutional Court to review the motion.

The government has already said it would seek a constitutional review of the referenda motions.

If the National Assembly calls a referendum, it would likely be held in January 2013, Virant added.