Scores of opposition MPs have resigned from Pakistan's national parliament and provincial assemblies in protest at Saturday's presidential election.
The opposition hopes to render the election meaningless
They insist that President Pervez Musharraf is ineligible to stand.
Meanwhile two rival candidates for Saturday's election have filed fresh petitions in the Supreme Court against Gen Musharraf's candidacy.
Last Friday the court dismissed a number of petitions, in a move seen as a major victory for the president.
The president is elected by MPs from the national assembly and Pakistan's four provincial assemblies.
Correspondents say that the resignations make it even more certain that Gen Musharraf will win the vote.
Members who resigned from the assemblies on Tuesday were drawn mainly from the alliance of Islamic parties, the MMA, and the PML-N party of former Prime Minister Nawaz Sharif.
Gen Musharraf looks certain to win Saturday's election
The BBC's M Ilyas Khan in Karachi says there were 86 resignations from the national assembly, 46 from the Punjab provincial assembly, 25 in Balochistan and seven in Sindh.
"We are handing over the resignations today because we consider the election of the president is illegal and unconstitutional," one leading MP, Liaquat Baloch, said, the AFP news agency reports.
The opposition had hoped to dissolve the North West Frontier Province assembly, which it controls, but this has been stalled by delays in tactics, correspondents say.
The MPs hope the resignations will make the presidential election be seen to be meaningless.
"This is the first step to discredit the election process," said former cricket star and MP Imran Khan, whose party is part of the opposition APDM alliance.
The country's biggest party is the Pakistan People's Party (PPP) of former Prime Minister Benazir Bhutto. It is not taking part in the boycott.
The PPP has been in talks with Gen Musharraf over a power-sharing agreement.
Parliament must now function without an opposition
The petitions filed by lawyers representing two candidates standing against President Musharraf, retired Judge Wajihuddin Ahmed and Makhdoom Amin - vice chairman of the PPP - say that the president is not eligible to stand while also remaining head of the army.
The petitions state that the Election Commission was wrong to approve his nomination papers over the weekend.
"We are hopeful for justice," lawyer Tariq Mahmood told the Associated Press news agency. "We have a strong case against President Musharraf."