Liberals and seculars in Egypt were alarmed on Thursday when President Mohamed Morsi assumed sweeping powers for himself, shielding his government from legal challenges until a new parliament is elected.

Presented as a move to “protect the revolution,” the Islamist president also decreed that an assembly that is tasked with rewriting the Constitution as well as the upper house of parliament are shielded from prosecution. Both bodies are dominated by members of Morsi’s Muslim Brotherhood party.

The decree also gave the constitutional panel two more months to complete its work, meaning that parliamentary elections could be pushed back to February of next year. The panel has faced a raft of legal challenges while many secular members stepped down, complaining that their voices were not being heard by the Islamist majority.

The present constitution, which dates back to Egypt’s military dictatorship, must be rewritten before there can be new elections. The nation’s highest court dissolved the legislature in June after it ruled illegitimate a third of the parliamentary elections that took place earlier this year. Morsi has since ruled as a strongman in the vein of President Hosni Mubarak who was deposed last year in a popular uprising and army coup.

Liberal activists, including former International Atomic Energy Agency chief Mohamed ElBaradei and former Arab League chairman Amr Moussa, both of whom stood as candidates in Egypt’s presidential election in May, announced protests in Cairo’s central Tahrir Square to demonstrate against the Muslim Brotherhood president who is described by them as a “new pharaoh”.

“Morsi is a ‘temporary’ dictator,” read the banner headline in Friday’s edition of independent daily Al-masry Al-youm.

Morsi’s supporters planned a counterprotest outside the presidential palace in Heliopolis in the north of the capital. They argue that Morsi’s power grab was necessary to eradicate vestiges of the old regime and prevent obstructionist judges from undermining Egypt’s transition to democracy.