Egypt's Muslim Brotherhood has defended its decision to run its deputy leader in the upcoming presidential election, despite alleged splits within the movement and accusations that it is trying to monopolise power.

The Brotherhood backtracked on an earlier pledge not to contest May's presidential election by announcing on Saturday that it would field deputy leader Khairat al-Shater.

"There is no intention to assert control," said Mohammed Morsi, head of the Brotherhood's political arm, the Freedom and Justice Party (FJP), which dominates Egypt's parliament and the senate.

"We are only present in what has been elected ... in parliament, in syndicates," he said on Tuesday, adding "This is the people's will. Does anyone want to oppose the people's will or prevent it?"

Mohammed Badie, the Brotherhood's supreme guide, dismissed reports that the movement had been almost evenly split on nominating Shater, a multi-millionaire businessmen who spent years in prison during president Hosni Mubarak's rule.

"It was a majority [that supported Shater's nomination]. And, unfortunately, all the numbers mentioned are wrong," he said of the vote by the movement's consultative assembly to nominate Shater.

"You can't imagine the number of faxes and messages I received on my phone showing unprecedented support for this decision," Badie said.

Shater himself said in February that he would not be running for president, adding the the Muslim Brotherhood would not have a candidate in the poll.

"We will not nominate a candidate from the Muslim Brotherhood. We'll announce who we will support just before nominations close," he said last month.

Power-grab

The Brotherhood's decision to run Shater opened a rare public rift in the movement, with one leading parliamentarian cautioning that it was over-reaching.

The movement had previously expelled former senior member Abdel Moneim Abul Fotouh for nominating himself for president and suspended his active supporters.

"I oppose the Brotherhood's nomination of one of its own for the presidency," wrote Mohammed al-Beltagi, an FJP parliamentarian, on his Facebook page.

"It harms the Brotherhood and the nation, to have one faction assume all the responsibility under these conditions," he wrote.

The movement faces a backlash over its domination of a panel tasked with drafting the country's new constitution.

Liberals, representatives of the Coptic Christian community and the Islamic Al-Azhar institute are boycotting the constituent assembly because of their disproportionate representation.

The new constitution will replace the one suspended by the ruling military which took power after Mubarak's ouster in an uprising last year.

An FJP parliamentarian said the movement nominated one of its leaders for president because it feared that it would lose support among the electorate if it did not have the executive power to implement its campaign promises.

"We need to implement our programme or we will lose votes. We initially approached three candidates from outside the group," he said, speaking on condition of anonymity.

The FJP is locked in a battle with the ruling generals to sack the military appointed candidate and replace it with an FJP-led government, which the group wants to give more powers to in the new constitution.

The Egypt Independent reported on Monday that there are calls among public figures for the head of Egypt's ruling military, Field Marshal Hussein Tantawi, to run for president.

There's a possibility that the military might also dissolve the current constitutional constitutional council, using its executive powers to create a new one.