Co-founder of the April 6 Youth Movement Ahmed Maher announced on Thursday he would freeze his membership of the Constituent Assembly on 18 November.
Maher said he had made the decision because the assembly had "ignored all proposals made by civil forces, political movements and civil society organisations."
He criticised how the assembly had been functioning, especially in light of the decisions on Wednesday and Thursday to pass certain articles without adequate debate.
Additionally, Maher criticised the short period of debate held on each article of the draft constitution so far and the decision to allow substitute members to vote on articles, in breach of earlier agreements.
He said he would need a number of guarantees before he would consider returning to the assembly.
He stated that all sessions held over the last week should be declared void and be held again. He added that the drafting committee would have to change its membership to allow for more diversity, and the drafting process would have to be extended for another three months at least. He also added that a clear and suitable timetable would have to be set for the completion of the consitution.
The assembly has been threatened with withdrawals, particularly from non-Islamists members, for many weeks.
On Wednesday, thirteen members said they would not play any further role at the constitution-drafting body. Some threatened to withdraw completely. They said they had taken the action in protest at the way debates were being managed.
The thirteen included former Arab League secretary-general Amr Moussa, liberal Wafd Party leader Sayed Badawi and Ghad Al-Thawra Party leader Ayman Nour.
The beleaguered assembly has already suffered a number of withdrawals since 11 June, when the 'Egyptian Bloc' parties – including the Free Egyptians, the Egyptian Social Democratic Party and the leftist Tagammu Party – initiated a walk-out, followed by the Karama Party, the Socialist Popular Alliance Party and the Democratic Front Party, to allow greater representation for women, young people and Coptic Christians, while also registering their objection to "Islamist monopolisation" of the assembly.
In late September, Nasserist Hamdeen Sabbahi and reform advocate Mohamed ElBaradei also called for a boycott of the assembly because it was “incompetent.”
The assembly is still facing the risk of dissolution by court order due to a case challenging the constitutionality of the law which set the criteria for choosing its members. The 100 assembly members were chosen by the now-dissolved parliament, which was ruled unconstitutional by the High Constitutional Court (HCC) in mid-June.