Egypt’s liberals and leftists vowed Sunday to boycott a crucial body tasked with writing the nation’s constitution, accusing Islamist parties of trying to dominate the process as the country lurched toward a political crisis.

Early Sunday, after a lengthy voting session, the parliament chose the 100-member body that will write the document. The constitution will delineate the powers of the once all-powerful president and the parliament and define the role of religion and minority rights in post-Hosni Mubarak Egypt.

Liberals and leftists accused the two most powerful Islamist parties of packing the assembly with their supporters to ensure a constitution steeped in Islamic ideology. Islamists took more than 70 percent of legislative seats. The Muslim Brotherhood’s Freedom and Justice Party alone has nearly half of the seats in the newly elected parliament.

“We are going to boycott this committee, and we are going to withdraw and let them make an Islamic constitution. We are going to continue struggling for a secular Egypt in the streets,” said Mohammed Abou el Ghar, head of the Social Democratic Party, who was elected to the assembly but has resigned his post. “We agreed that this will be a balanced committee and it will represent all views of Egypt. But as you can see, there is no representation of secular Egypt.”

As agreed by the parliament last week, 50 members were chosen from the parliament and 50 members were chosen from other sectors of society. Ghar and other liberals and leftists said the panel has little representation of women or Egypt’s minority Christian community. Ghar said his party, along with the liberal Free Egyptians and the youth party known as “the Revolution Continues,” all agreed to withdraw from the constitution-writing process. At least eight people had resigned their positions on Sunday and Ghar expected others to follow.

Ghar said it was unfair that a group of lawmakers chosen in one election would draw up a document that could last decades.

“Who knows what the next election will bring. Maybe the liberals and leftists will be the majority. So how can Egypt’s constitution be written by a group of people who happen to be elected at one point in history?” he said in an interview.

The Revolutionary Youth Union, a group of activists, issued a statement accusing the Freedom and Justice Party of putting its interests “before those of the country,” and “following the same methods of the dissolute National Democratic Party [Mubarak’s Party] in controlling all positions and all political matters in the country alone, purposefully eliminating everyone outside the Brotherhood.”

The group urged Egyptians to join a protest Wednesday outside parliament when the constituent assembly is scheduled to meet for the first time.

The Freedom and Justice Party fired back at the accusations, declaring that the assembly “included all factions, directions and institutions,” and was representative of Egypt’s artists, political parties, journalists, prominent figures and Christian and Muslim institutions.

“The constituent assembly was not taken over by the Freedom and Justice Party as some have said,” the statement said.

According to the rules agreed on by parliament, if someone resigns from the assembly, a person selected from a list of 20 alternates will replace them.

Special Correspondent Ingy Hassieb contributed to this report.