Egypt's biggest political group the Muslim Brotherhood clashed with the country's army leaders on Thursday, accusing them of trying to "marginalise" parliament over the writing of a new constitution.

The army meanwhile appointed a panel tasked with drafting a law to name the group who will draft the constitution, pointedly ignoring calls by the Brotherhood to leave the matter to parliament, where Islamists enjoy a majority.

The 30-member advisory board, which comprises intellectuals and politicians, will also discuss the premises of Egypt's presidential elections scheduled for june 2012, the ruling military authorities said in a statement.

Mohammed el-Baltagui, one of the leaders of the Brotherhood's political party, said earlier the movement had pulled out of a contact group with the army leaders who have been in power since the toppling of Hosni Mubarak in February.

"We consider that any attempt to marginalise the parliament or to reduce its prerogatives in favour of any other unelected entity is a move to bypass the will of the people," he told AFP.

On Wednesday, in comments to a small group of foreign journalists, a member of the ruling junta said the army would have a final say over those appointed to a 100-member panel tasked with writing a new constitution next year.

"This is the first stage in our democracy," Major General Mukhtar al-Mulla was quoted as saying by The Guardian newspaper. "This is not out of mistrust of the parliament," he added.

The Brotherhood, which emerged as the biggest winner in the first stage of the just-concluded parliamentary elections, wants the assembly to oversee the constitution writing process.

Analysts had forecast a fierce power struggle between the new civilian political powers that have emerged since the fall of Mubarak and the ruling army generals charged with managing the country's democratic transition.

Millions of Egyptians flocked to the polls at the start of the first phase of parliamentary elections last week, with the majority opting for Islamist parties.

The more moderate Brotherhood, banned for decades by Mubarak, won 37 percent of votes cast for parties, with the ultra-conservative Islamic fundamentalist party Al-Nur picking up about 25 percent.

The Brotherhood also won the vast majority of votes cast for individual candidates.

The prospect of an Islamist-dominated parliament has raised fears among secular liberals about civil liberties, women's rights and religious freedom in a country with the Middle East's largest Christian minority.

They fear that Islamist parties in the new assembly will use their influence to ensure an overtly religious and conservative new constitution.

Mulla justified the army's oversight of the constitution process because the parliament would not be representative of "all the Egyptian people."

"What we are seeing is free and fair elections ... but they certainly don't represent all sectors of society," The Guardian quoted him as saying.

Under the current timetable, the writing of a new constitution was meant to be undertaken by a 100-member panel named by the upper and lower houses of parliament once they have been elected by March.

In another area with potential for tension, the Muslim Brotherhood has also said it expects to be asked to form a new interim caretaker government if it emerges as the biggest power in parliament.

The head of the ruling Supreme Council of the Armed Forces (SCAF) swore in a new military-backed cabinet on Wednesday headed by a former prime minister from the Mubarak era, 78-year-old Kamal al-Ganzuri.