“We documented a set of irregularities that are clearly evidence of systemic violations,” said Amr Hamzawy, an NSF leader and political science professor. “We would like the responsible party to investigate and report the conclusions before the final results of the referendum are announced,” he added, referring to Egypt’s High Elections Commission.

The NSF said it had compiled a list of 1,500 violations in the referendum’s first round on Dec. 15 and said a similar number of abuses occurred Saturday. Charges include voters being turned away and judges who served as observers turning up late at voting centers where the constitution was expected to fail.

NSF leaders warned that the constitution amounted to President Mohamed Morsi’s first step in a plan to build an Islamist dictatorship. “We see that our people are on the verge of a series of laws that will ravage general freedoms and will humiliate the poor in this nation,” said Hamdeen Sabahi, one of the NSF’s leaders and a former presidential candidate.