Opponents of Egyptian President Mohamed Morsi have staged protests in Cairo against an Islamist-backed draft constitution that has divided Egypt but looks set to be approved in the second half of a referendum this weekend.

Around 2,000 protesters outside the presidential palace on Tuesday chanted “Revolution, revolution, for the sake of the constitution” and called on Morsi to “Leave, leave, you coward!”

Morsi obtained a 57 per cent “yes” vote for the constitution in the first part of the referendum on December 15, state media said, a total that was less than he had hoped for.

The opposition, which says the law is too Islamist, will be encouraged by the result but is unlikely to win the second part on December 22.

The second round is to be held in districts seen as even more sympathetic towards Morsi’s Muslim Brotherhood.

The National Salvation Front opposition coalition said there were widespread voting violations last Saturday and called for protests to “bring down the invalid draft constitution”.

The Ministry of Justice said it was appointing judges to investigate complaints of voting irregularities, but the secretary general of the electoral commission, Mahmoud Abu Shousha, vehemently rejected the opposition’s claims that fake judges oversaw voting in some polling stations.

If the constitution is passed, national elections can take place early next year, Morsi’s camp argues will bring stability to Egypt after months of turmoil following the revolution that toppled Hosni Mubarak in 2011.

The opposition is scathing of the document, which was written largely by Islamists, believing it weakens human rights protections, particularly for women, and sets the stage for a creeping advance towards Islamic sharia law.

Judicial challenge

Egypt’s public prosecutor resigned on Monday under pressure from his opponents in the judiciary, dealing a blow to Morsi and drawing an angry response from his supporters in the Muslim Brotherhood.

In a statement on its Facebook page, the group that propelled Morsi to power in an election in June, said the

forced resignation newly appointed of public prosecutor Talaat Ibrahim Abdallah was a “crime” and authorities should not accept the resignation.

The referendum has had to be held over two days because many of the judges needed to oversee polling staged a boycott in protest. In order to pass, the constitution must be approved by more than 50 per cent of those voting.

Many of Egypt’s 21,000 judges were keeping up their pressure on Morsi, charging that he was trying to undermine their independence.

In their boycott of the supervision of the second round of voting, 2,600 judges on Monday joined an estimated 12,000 judges who already boycotted the first round.

Morsi’s challenge

The closeness of the first referendum vote and low turnout give Morsi scant comfort as he seeks to assemble support for difficult economic reforms.

“This percentage … will strengthen the hand of the National Salvation Front and the leaders of this Front have declared they are going to continue this fight to discredit the constitution,” said Mustafa Kamel al-Sayyed, a political science professor at Cairo University.

Morsi, said Sayyed, is likely to become more unpopular with the introduction of planned austerity measures.

To tackle the budget deficit, the government needs to raise taxes and cut fuel subsidies. Uncertainty surrounding economic reform plans has already forced the postponement of a $4.8bn loan from the International Monetary Fund.

The Egyptian pound has fallen to eight-year lows against the dollar.