State media, however, already say the draft charter has received enough support from voters.
While demonstrators have shouted their anger over the constitution in protests that have at times turned violent, it appears the silent majority has spoken at the polls, the CBC's Derek Stoffel reported from Cairo.
"We all want stability," one female supporter said, translated from Arabic. "We want our children to be safe. We want peace and security."
The opposition, however, claims the new constitution, backed by Islamist President Mohammed Morsi's Muslim Brotherhood, seeks to enshrine Islamic rule in Egypt, and accuses the Islamists of trying to monopolize power.
On Sunday, after the Muslim Brotherhood claimed the draft charter passed with 64 per cent of the vote, Egypt’s opposition called for an investigation into allegations of vote fraud in the referendum.
Opposition says it has filed complaints
“The referendum is not the end game. It is only a battle in this long struggle for the future of Egypt,” said the National Salvation Front, the main opposition group. “We will not allow a change to the identity of Egypt or the return of the age of tyranny.”
The opposition front said it has filed complaints to the country’s top prosecutor and the election commission asking for an investigation.
The investigation into allegations of vote violations — including insufficient supervision by judges and women being prevented from voting — could delay the release of the final referendum results, the CBC's Dominic Valitis reported from London.
Turnout for the vote was 32 per cent of Egypt’s more than 51 million eligible voters, according to the Muslim Brotherhood. That was significantly lower than other elections since the uprising ended in February 2011.
The opposition has pointed to the low turnout as well as allegations of violations in the voting to cast doubt on the legitimacy of the referendum.