Egyptian demonstrators shout slogans during a protest against Mohamed Morsi in front of the presidential palace in Cairo. Reuters

President Mohamed Morsi's decision to rescind most of the controversial decree awarding himself untrammelled powers failed to stem the wave of protest against him in the run-up to a critical referendum on the shape of the new Egyptian state.

The opposition National Salvation Front (NSF) declared on Sunday night it would boycott the vote on the new constitution, arguing that it was impossible against a background of Muslim Brotherhood "intimidation". The referendum was "grossly irresponsible" and would cause "cause further division and polarisation", it claimed.

On Cairo's streets protesters demonstrated continuing defiance with a march on the presidential palace, now heavily guarded by the army and surrounded by a cement wall to keep people away from the perimeter. The opposition called for fresh protests on Tuesday, while insisting it still recognised Morsi as the elected president.

Morsi supporters held marches near the Muslim Brotherhood headquarters in Mokkatam in support of the referendum and a yes vote, a reminder that Egyptian politics remains finely balanced and volatile.

"The referendum will cause further division and polarisation and the Front refuses the draft constitution which cements presidential oppression and tramples freedoms and liberties" said Sameh Ashour, head of the Lawyers Syndicate, in a statement on behalf of the NSF coalition.

"To have a referendum now with the threat of Muslim Brotherhood militias and threats and intimidation against the opposition, and absence of security is grossly irresponsible. The Front calls on Egyptians to continue to peacefully protest on Tuesday against the constitution and a president who ignores his people."

After over two weeks of stand-offs and street battles with the opposition, the government called a dramatic midnight press conference on Saturday to announce Morsi had rescinded his contentious 22 November decree which had given the presidency extensive powers beyond the control of Egypt's courts. A new decree was announced, with many of the most controversial elements absent, but the president's judicial immunity remains.

The government insisted that the referendum would go ahead on 15 December as planned, and Morsi issued a decree giving the army powers of arrest and detention of civilians until the result of the referendum is announced.

On Sunday Morsi used legislative powers he holds in the absence of parliament to implement tax rises on more than 50 goods, including fuel, electricity, steel, cement and luxury items such as cigarettes and alcohol – a 100% rise for beer and some other beverages. The increases come as part of economic reforms being introduced ahead of the 19 December deadline for International Monetary Fund approval of a $4.8bn loan.

Last month's decree granted Morsi and the country's constituent assembly immunity from judicial review only weeks before Egypt's supreme constitutional court was due to give its verdict on the validity of the assembly. It also included a catch-all article giving Morsi authority to take any measure he deemed fit to safeguard national security.

Hundreds of thousands of protesters marched to Tahrir Square and to the presidential palace, denouncing the decree as dictatorial. Morsi's supporters insisted it was necessary to safeguard the Egyptian revolution from forces of reaction loyal to the old Mubarak regime.

The assembly – then without liberal and Christian representatives who had withdrawn – rushed to finalise the draft and officially hand it to Morsi, who then called for a referendum to take place this Saturday.

Further protests and counter protesters by Morsi supporters occurred and violence broke out last Wednesday when Morsi supporters sanctioned by the Muslim Brotherhood's political arm, the Freedom and Justice Party, forcibly dispersed an opposition sit-in. The resulting clashes have claimed eight lives with more than 700 injured.