CAIRO (AP) -- Egypt's president ordered parliament's upper chamber to convene after the release of official results of a referendum on an Islamist-backed constitution that gives temporary legislative powers to the traditionally toothless chamber.

The results had been expected on Monday but were not released and the electoral commission has not yet set a date to announce them. The Muslim Brotherhood, the main group that backed the charter, said it passed with 64 percent of the vote - a result likely to be confirmed by the official result.

Parliament's upper house, the Shura Council, cannot convene before the official word that the constitution has passed.

The new constitution would give the Shura Council powers to legislate until the lower house is elected within the next two months. President Mohammed Morsi has held legislative powers for months now since a court disbanded the lower house of parliament.

Over the weekend, Morsi appointed 90 members to the Islamist-dominated Shura Council, in an attempt to make the body more representative.

The 90 include at least 30 Islamists and a dozen minority Christians. The council now has a total of 270 members, two-thirds of them elected. Critics, however, say most of the representatives are either Islamists or their supporters.

The council was elected last winter in a vote with an extremely low turnout of less than 10 percent of Egypt's 51 million eligible voters.

The council is expected to prioritize the passing of a new law on the rules for parliamentary elections. The former lower house, the first to be elected after the uprising that forced President Hosni Mubarak out of office nearly two years ago, was dissolved after a court order ruled the law governing election of its members was unconstitutional.

The passage of the disputed constitution following a month of political bickering has left Egypt more polarized and poised for continued tension. The opposition has already vowed to challenge the results of the referendum, alleging fraud and violations in the voting.

Critics say the new constitution seeks to enshrine Islamic rule in Egypt and accuses the Islamists of trying to monopolize power.

They say the charter does not sufficiently protect the rights of women and minority groups and empowers Muslim clerics by giving them a say over legislation. Some articles were also seen as tailored to get rid of Islamists' enemies and undermine the freedom of labor unions.

Morsi and his supporters say the constitution is needed to restore stability in the country, restore an elected parliament and build state institutions.