Opposition groups in Egypt have said they will boycott a referendum on new rules for presidential elections.
Cairo has seen demonstrations for and against President Mubarak
They argue that the new election rules are designed to improve the country's image without bringing about real democratic change.
The referendum is due to be held on the 25 May on a constitutional amendment that would open presidential elections to more than one candidate.
The amendment has already been approved by the Egyptian parliament.
Egypt's government is urging a "yes" vote, saying the amendment heralds a new era of democracy.
But the three main legal opposition parties, the Wafd, the Tagammu and the Nasserist party, are all now urging Egyptians to boycott the referendum.
The banned Muslim Brotherhood, which widely seen as the most popular political organisations in Egypt, has also called for a boycott.
Ruling party dominance
The opposition argues that the proposed new rules for presidential elections contain too many conditions to meet for any candidate from outside the ruling National Democratic Party of President Hosni Mubarak.
The law imposes tough conditions on such independent candidates - they would have to receive the backing of at least 65 members of a parliament overwhelmingly dominated by the ruling party.
BBC Cairo correspondent Heba Saleh says the impact of the opposition's call for a boycott will be hard to gauge.
One reason for is that, apart form the Brotherhood, the opposition parties have very little popular support.
'Turned off politics'
In addition, turnout rates are usually very low in Egyptian elections. Many people do not bother to vote because they say it will not change anything.
Analysts argue that decades of election rigging and political stagnation have turned most Egyptians off politics.
Mr Mubarak's announcement in February that the constitution would be changed to allow contested presidential elections was hailed as a reform.
It came under domestic and US pressure to democratise the political system.
The next presidential election is scheduled for September, but Mr Mubarak has not said whether he plans to seek a fifth, six-year term in office.