Nobel Laureate Mohamed ElBaradei urges President Mohamed Mursi to be a president for all Egyptians.
The former director of the International Atomic Energy Agency told the Islamist president on Twitter: "In light of Egypt's evident, and dangerous, division, will you realize the necessity of being a president for all Egyptians?" reminding him that ruling is a responsibility.
"Referendum 1st round: country split, flagrant irregularities, low turnout, with Islamists on the rise. Illiteracy remains a hurdle," ElBaradei added on his Twitter account.
The founder of the liberal Dostour Party wondered whether a referendum that took place amid violations, violence and without full judicial supervision and security was the way for stability or a tampering with the country's destiny.
"The nation is becoming more and more divided. State foundations are trembling. Poverty and illiteracy are the fertile ground for selling religion. The level of awareness is growing swiftly and Egypt's revolution is not far-fetched," the prominent opposition figure said.
Meanwhile, the National Salvation Front has said that it would not recognize any results but the official ones announced by the judicial committee that is overseeing the referendum.
The first round of a referendum on a draft constitution written by an Islamist-dominated assembly kicked off on Saturday while the second round is scheduled for December 22.