Top PASOK deputy Evangelos Venizelos, a veteran ex-minister and the party’s leader up until last week, on Saturday told Parliament that the government’s surprise proposal for a referendum needs the approval of three-fifths of the legislature’s 300 deputies.

Venizelos, a constitutional law expert by training, said the snap referendum called by leftist PM Alexis Tsipras only hours earlier deals with the country “strategic course”, and as a result, mandates an increased majority of Parliament MPs in order to pass.

He said a simple majority (150+1) would be unconstitutional, in this case.

“What you’re (the SYRIZA government) doing is an attempt to pilfer the vote, essentially a coup attempt,” he charged in a forceful address.

Venizelos also warned the government that a “yes” to the drachma — alluding to the specter of Greece exiting the common currency — means uncertainty and insecurity.

“Are the two documents, the Greek proposal and the creditors’ proposal, for which you want a referendum, official?” he asked, adding: “What are the differences (between the two documents)?”