An influential group of Egyptian judges says it will not oversee a December 15 referendum on a new constitution, a move that could undermine the legitimacy of the charter supported by the nation's Islamist president.

In a statement published Sunday by state news agency MENA, the Judges Club said its members unanimously agreed to boycott the referendum, a voting process that Egyptian judges usually supervise.

Many Egyptian judges went on strike last month to protest President Mohammed Morsi's decree barring courts from challenging his decisions. The judges of Egypt's top court joined them on Sunday, saying they have suspended their work indefinitely because of what they called “psychological and physical pressures.”

The judges said they were afraid to enter the Supreme Constitutional Court for a Sunday session in the midst of a rally by hundreds of pro-Morsi Islamists outside the building. The judges had planned to issue rulings that could have dissolved two Islamist-controlled assemblies — the panel that drafted the new constitution and the upper house of parliament.

Constituent assembly members adopted the charter Friday after several days of racing to finalize the document before the top court could rule on whether to annul their body. Christians and liberals boycotted the assembly, complaining that Morsi supporters were hijacking the constitution-drafting process.

President Morsi called for the December 15 referendum on the constitution after receiving the document Saturday. The draft boosts the role of Islamic law in Egypt and makes no explicit mention of women's rights. That has led rights groups and liberal Egyptians to fear a potential erosion in civil liberties.

Mr. Morsi said his November 22 decree granting himself sweeping powers will end immediately after the referendum.

More than 100,000 Islamists gathered in Cairo Saturday for a pro-Morsi rally organized by the president's Muslim Brotherhood movement. In a rival protest, opposition activists camped out in Cairo's Tahrir Square for a 10th day, vowing to remain until President Morsi rescinds his decree, which they see as giving him near dictatorial powers.