(Reuters) - Egyptian liberals and leftists wary of Islamist dominance of an assembly drafting a new constitution said on Tuesday they would write their own, deepening a row overshadowing a major element of the transition from President Hosni Mubarak´s rule.

Liberals who have quit the 100-member assembly in protest at its make- up were among those who signed a statement that pledged to write an alternative constitution to the one being drafted by the official body, which was formed at the weekend.

"We shall undertake this duty from outside the official assembly in collaboration with all the segments of society and experts that should have been included from the beginning," said the statement, released at a news conference where one speaker after another accused the Islamists of seeking to dominate.

The row has raised doubts over the credibility of a process designed to set the rules for how Egypt is governed, adding a new challenge to the ruling military´s transition plans.

The Islamists secured a major say in the constitutional assembly´s composition thanks to their strong position in parliament, where the Muslim Brotherhood and the more hardline Nour Party won some 70 percent of seats in recent elections.

Liberals, leftists and others say the poll result should not decide the make-up of a body that will write a constitution meant to last far longer than a parliamentary term. Women, young people and minority Christians are under-represented, they say.

"The political Islamic current has given itself the right to monopolize the writing of the constitution, excluding the other factions of Egyptian society," Ahmed Said, head of the liberal Free Egyptians Party, said at the meeting.

Mostafa El Gendy, a liberal and a member of the Revolution Continues group, told Reuters: "The constitution is for all Egyptians, to be participated in by all Egyptians."

LEGAL COMPLAINTS

The Muslim Brotherhood disputes accusations that Islamists dominate the Constitutional Assembly, saying it contains 48 Islamists, 36 from parliament and 12 from outside. Their opponents say a score of other members have Islamist leanings.

The Brotherhood, founded in 1928, has said the criticism amounts to an attempt by the minority to impose its will on an elected majority. "Thirty million people elected those MPs. How come they shouldn´t be part of the assembly?" asked Abdel Khaleq al-Sherif, a member of the Brotherhood´s advisory council.

Field Marshal Mohamed Hussein Tantawi, head of the military council ruling Egypt since Mubarak was toppled, met politicians on Tuesday to try to resolve the crisis, an army official said.

The military council is due to hand power to a new president at the end of June, completing a transition to civilian rule.

A Cairo court convened on Tuesday to hear legal complaints filed by Egyptians over the formation of the constitutional assembly, and about 150 protesters gathered outside.

"We didn´t die so the Brotherhood could write the constitution," read one of their banners.

Hafez Abou Saeda, head of the Egyptian Organization for Human Rights, who was among the crowd, said: "It (the assembly) poses great danger because it means two parties with Islamist orientations will divide amongst themselves the constitution, meaning they can restrict rights and freedoms.

"They can seek to implement a system of government that gives more powers to the majority party, turning our system from a presidential one to a parliamentary one which leads to control of the upper and lower houses of parliament and the government."

Some members of the Brotherhood and the Nour Party have also criticized the way the assembly was formed.

"I call on the Muslim Brotherhood and the Salafi Nour Party, to which I am honored to belong, to open the door to communication and dialogue," said Yasser Salah El-Kadi, an Islamist MP who attended Tuesday´s news conference. (Additional reporting by Tamim Elyan and Ashraf Fahim; Writing by Tom Perry; Editing by Alistair Lyon) (© Thomson Reuters 2012. 03/27/12)