An Egyptian administrative court has suspended general elections that were scheduled to begin in April.
The court said the electoral law needed to be reviewed by the Supreme Constitutional Court to determine whether it conformed to the constitution.
President Mohamed Morsi had said the polls would begin on April 22, taking place in four stages over two months.
The elections have been boycotted by the main opposition, amid continuing street protests.
The National Salvation Front (NSF) has said the electoral law favors Mohamed Morsi’s Islamist allies – a claim denied by the president.
The NSF has also expressed concerns that the election will not be free and fair.
Egypt remains sharply divided between Islamists and their liberal and secular opponents.
More than 70 people have been killed in violence between security forces and protesters since February, following the second anniversary of the revolution that ousted President Hosni Mubarak.
On Wednesday, the security head in the city of Port Said was dismissed following renewed clashes between demonstrators and police.
The coastal city has seen sporadic violence since January, when death sentences were handed down to 39 people imprisoned over football violence last year which left more than 70 people dead.
The administrative court said it had acted because the Shura Council – the upper house of parliament – had not returned the amended electoral law to the Supreme Court for final review.
Instead, the court said, the Shura Council had sent the law to President Mohamed Morsi for ratification.
Mohamed Morsi’s office has so far made no public comment on the court’s decision. The president can appeal against the ruling.
Egyptian courts have made a number of decisions that have gone against the president and his Muslim Brotherhood movement, further complicating the country’s political crisis.
In June, the lower house was dissolved after the Supreme Constitutional Court ruled that one of the laws under which the elections were fought was not legitimate.
In the last elections, in January 2012, Islamist parties won an overwhelming majority, with the Freedom and Justice Party of the Muslim Brotherhood movement taking the biggest share.electoral law, general elections, Hosni Mubarak, mohamed morsi, muslim brotherhood movement