Aljazeera's correspondent in Cairo reported on Tuesday that the leftist Tagammu party and the Arab Nasiri party decided to boycott the Egyptian presidential election scheduled for 17 September.
While the boycott decision by the Tagammu party includes both the nomination of candidates and voting, the leader of the Arab Nasiri party said the group will not get involved in an election process that it calls a "sordid hoax".
Rifaat el-Said, secretary-general of the Tagammu Party, told a news conference: "We don't want to be bit actors in a play the outcome of which is known in advance."
"The general secretariat decided by a majority not to nominate anyone from the party leadership for the presidential election and to boycott these elections," a statement said.
"The government maintains despotic conditions, has stood against any constitutional or political reform and insists on no judicial supervision (of the elections)," it said.
President Hosni Mubarak, 77 and in power since 1981, is expected to seek a fifth six-year term in the elections, the date for which could be announced next Sunday.
They will be the first elections in Egypt with more than one presidential candidate, after a constitutional amendment in May abolished the system of referendums on a single candidate chosen in advance by parliament.
"The government maintains despotic conditions, has stood against any constitutional or political reform and insists on no judicial supervision (of the election)"
But the only prominent politician likely to challenge Mubarak is Ayman Nour of the liberal Ghad (Tomorrow) Party, who was detained earlier this year and is on trial on forgery charges that he and his party say are politically motivated.
Said said the Tagammu had given the authorities a chance to fulfil their promises of a level playing field for the presidential elections but had now abandoned hope.
The party had complained five times that local authorities had removed party banners while leaving in place those of Mubarak's National Democratic Party, he said.
State newspapers and television stations rarely mention opposition groups or their activities, while giving extensive coverage to all Mubarak's public appearances and portraying him as a wise and benevolent leader.
The liberal Wafd Party is expected to follow the Tagammu's example within days, political sources said.
In the past week, two prominent independents have announced that they are abandoning their symbolic campaigns for the presidency on the grounds that the government is not serious about holding free and fair elections.
The independents, sociologist Saadeddin Ibrahim and feminist writer Nawal el Saadawi, would not have been on the ballot anyway because the constitutional amendment sets strict conditions for non-party candidates to stand.
The only prominent politician left
is Ayman Nour
The banned but tolerated Muslim Brotherhood, widely seen as the strongest opposition force, says the restrictions on independents are aimed at stopping the movement from fielding a candidate.
A visiting US official said last week that Washington believed the government was serious about political reform.
The official, Deputy Secretary of State Robert Zoellick, said he had again pressed the Egyptian government to let international observers monitor the elections. The government has not taken a position on the proposal.