Egypt's new Islamist-dominated parliament voted on Saturday to select members for a body that will draft a new constitution but liberal and leftist MPs withdrew, protesting that the nation's diversity would not be properly represented.

The document could decide which branch of state will effectively rule the Arab world's most populous state for years to come after decades of autocracy that ended with Hosni Mubarak's fall to a popular revolt a year ago.

The constitution will define the balance of power between parliament and president, the role of Islamic sharia law in statute and society, and the political role of the military - in power since Mubarak's removal.

The Muslim Brotherhood's Freedom and Justice Party (FJP), which controls most seats in both chambers of parliament, said it aimed for an all-embracing constituent assembly.

In a statement the FJP said: The party's parliamentary bloc is keen to include all political and ideological streams in the assembly, as well as represent all sectors of Egyptian society ... including youth, women and (Christian) Copt representatives.

Those groups now occupy just a handful of seats, and liberals together hold less than one third of the mandates in parliament. Many of them say the Islamist majority is manoeuvring to eliminate alternative political streams and civil society from the 100-strong constitution-setting body.

According to a preliminary list of names published by Egypt's state news agency, the FJP took 25 of the 50 posts offered to those in parliament with other Islamists taking 13 places. Liberals, other parties and independents took the rest.

The remaining 50 places from outside parliament to make up the 100-strong assembly included legal experts, academics and union officials, as well as Islamic scholars and Christians, who account for about a tenth of Egypt's 80 million people.

The agency said the list of names still had to be confirmed.

In a statement, the liberal Egyptian Social Democratic Party said its pullout from the vote was to protest against the FJP's continuous attempts to marginalize minorities and civil forces, a process that is clearly against the sought democracy.

Basil Adel of the Free Egyptians, another liberal group, said his party also withdrew. He said the boycott included, in all, about 50 liberals, leftists and others from both houses.

FJP members of parliament, prior to the vote, named liberals among those they wanted included in the constituent body.

The lower house has 508 seats, of which 498 are elected. The upper house has 180 elected members plus a further 90 to be appointed. Only elected members can take part in the vote for the constituent assembly.

CRITICISM

Armed with popular legitimacy from Egypt's freest vote since army officers ousted the king in 1952, the Muslim Brotherhood and ultra-conservative Salafi Islamists now dominate parliament following a tortuous voting process that ended in January.

Most analysts agree that the Brotherhood, formed in 1928, is seasoned by decades of patient grassroots work and is unlikely to rush to impose purist Islamic codes, tear up Egypt's peace treaty with Israel or confront the United States.

But the Brotherhood has become more outspoken since the parliamentary vote. It has demanded that the military-backed prime minister and cabinet quit. Under the transition, the ruling army, not parliament, picks the government.

In a statement on Saturday, the Brotherhood again criticised Prime Minister Kamal al-Ganzouri, describing his government's performance as a failure. It was also critical of the army, saying its backing for the government raised questions about whether it wanted to abort the revolution.

Under Egypt's interim constitution, the new assembly must draft a new constitution within six months once it is formed. The new document will replace one that helped keep Mubarak in power for three decades and was a cornerstone of his rule.

The upper and lower house of parliament agreed in a meeting last week that lawmakers would select half the assembly's members from within their own ranks and pick the other 50 members from other parts of society.

That decision irked liberals, who said that although Islamists have a right to impose their will via a majority on legislation, they should not dominate an assembly that will draw up a permanent document to represents all Egyptians.

(Additional reporting by Edmund Blair and Shaimaa Fayed; Editing by Mark Heinrich)