Fresh opposition protests have been held outside the presidential palace in Cairo over the contentious Islamist-backed draft constitution that looks on course to be adopted after the second and final half of the referendum on 22 December.
Mursi's Muslim Brotherhood party and state media say that 57 per cent of voters have supported the draft constitution so far – according to unofficial figures – however Egypt's justice ministry has ordered a probe into allegations that voting irregularities were rife during the first half of the referendum on 15 December.
The investigation follows claims by the opposition National Salvation Front – an alliance of political parties led by liberal Mohammed ElBaradei – that the referendum was marred by numerous "irregularities and violations", including women being barred from polling stations and the use of fake judges.
Significantly, much of the judiciary is stepping up its challenge to Mursi's authority and the proposed charter which was rushed through parliament on 30 November. It came a week after a controversial decree that gave Mursi sweeping powers and which the judiciary felt undermined its authority.
On 17 December a group of top judges threatened to boycott supervision of the second round of the referendum unless the Muslim Brotherhood's "siege" of the Supreme Constitutional Court is lifted. The lack of cooperation from the judiciary poses a serious problem for the Mursi administration as polling must be overseen by judges if the polling results are to be validated.
The opposition fears that large Islamist constituencies in rural and upper Egypt could see the referendum passed on 22 December.
Voter turnout for the referendum has so far been low in Egypt, as well as among the half a million Egyptian expatriates who are entitled to vote in Egypt's 150 diplomatic missions abroad. Preliminary results showed that in Washington DC, more than 70 per cent of the vote was against the bill, while in the Saudi Arabian city of Jeddah more than 80 per cent was in its favour.
The renewed protests and mass marches in Egypt since Mursi announced his decree have rattled investor confidence and further disrupted the country's ailing tourist industry. The International Monetary Fund (IMF) has delayed a $4.8bn loan, and Germany has postponed indefinitely a $316m debt forgiveness plan.