The court also ruled that the new election law should be sent to the constitutional court for review.
Mohamed Gadaalah, a legal officer in the president’s office, said the government would abide by the court’s decision. He said the election law would be sent for review to the constitutional court as soon as possible.
But the move has cast further doubt on the fragile political process Mr Morsi has been trying to push through in the face of vehement opposition.
The main National Salvation Front opposition alliance wants the electoral law to be reviewed by the Constitutional Court as it considers it to be unfair and to give undue advantage to the Islamists who drafted it without input from other political groups.
The Constitutional Court has already reviewed the law once and sent it back to the Islamist-dominated Shura Council, which is serving temporarily as a legislature. The court called for amendments including changes to constituency boundaries to make for a fairer distribution of parliamentary seats. But the opposition is still complaining about what it alleges is gerrymandering by the Islamists to ensure maximum advantage for themselves.
An opposition spokesman told the Financial Times that constituencies with large numbers of Christians, who tend to vote for secular groups, have been merged with neighbouring districts to dilute the chances of non-Islamist parties.
Brotherhood deputies in the upper chamber had refused to send the law back to the Constitutional Court to ensure that the changes they have made met its requirements.
The NSF announced last week that it would boycott the poll saying that its concerns had been brushed aside by the Islamists. The alliance wants a government reshuffle before the poll to ensure the neutrality of the authorities overseeing the election. More specifically they want the ministers of the interior, youth, local government and supply (responsible for subsidised food) to be changed because they say these positions could be exploited to influence the vote.
So far, however, Mr Morsi has refused to reshuffle the government and Brotherhood spokesmen have accused the opposition of creating problems in order to cover up their weak support.
● An Egyptian court on Wednesday sentenced, Ahmed Ezz, a steel tycoon and prominent member of the ousted regime of Hosni Mubarak, to 37 years in prison and a $296m fine.
Mr Ezz was convicted of profiteering and squandering public funds. He is already serving a combined sentence of 17 years in connection with graft and money laundering.
The court that sentenced Mr Ezz found him guilty of making illicit gains of $740m over a decade through business deals involving Ezz Dekheila, a steel company in which he became the largest shareholder, and a smaller private company that he owns.