Egypt’s President Mohamed Mursi has called on all political powers to join a national dialogue aimed at resolving simmering tensions after a controversial new constitution was approved in a national referendum.

Official results show that the constitution was approved by about 63 per cent of voters, although turnout for the poll was only around 33 per cent.

In a televised address to the nation after Mursi signed the new constitution into law, he said he was considering possible changes to the cabinet and new incentives to attract investment into Egypt.

The constitution, drafted by an Islamist-dominated assembly, has been criticised by opponents of Mursi as being rushed through and lacking in detail or explanation of how the rights it codifies should be interpreted or upheld. Critics also fear that the document will favour Islamists.

The run up to the referendum was marked by widespread demonstrations by supporters of the president and his opponents, exposing the deep divisions within Egyptian society and the failure of the election of a new president to restore stability to the country.

Continuing political tensions has weighed heavily on the country’s economy. Ratings agency Standard & Poor’s downgraded Egypt’s credit rating from B to B- on 24 December blaming the political situation, and said further downgrades were possible if efforts to restore the government’s finances and economy growth continued to stall.

A $4.8bn IMF bailout package, considered vital to get the economy moving again, was postponed in mid-December as a result of the political row about a presidential decree that granted Mursi sweeping new powers. The rushed new constitution was intended to avert that crisis, but has simply shifted opposition anger to another area.

Protests against the constitution are planned for 25 January, the anniversary of the uprising against former ruler Hosni Mubarak, ousted in February 2011.