Cairo, Egypt (CNN) -- Egypt's largest opposition group, the Muslim Brotherhood, will boycott runoff parliamentary elections scheduled for Sunday, a member of the party said Wednesday.
Mohamed Beltagy, a member of the Muslim Brotherhood and a former legislative candidate, said the boycott is a protest against irregularities in the first round of voting last Sunday.
The party was wiped out Sunday, going from 88 seats in the legislature to zero.
Egypt's ruling National Democratic Party won 217 seats in the first round of voting, the semi-official Al-Ahram newspaper said.
The opposition parties won a mere handful of seats in the 508-seat parliament.
Twenty-seven candidates affiliated with the Muslim Brotherhood qualified for runoff elections. Muslim Brotherhood candidates run as independents because the group is illegal under to Egyptian law, which bans parties based on religion.
The runoff will involve 377 candidates from the National Democratic Party of longtime President Hosni Mubarak.
On Tuesday, the administration of U.S. President Barack Obama criticized the elections, saying there had been "numerous reported irregularities" and "restrictions on basic freedoms."
National Security Council spokesman Mike Hammer called the reports "worrying" and said the United States is "disappointed."
Critics had predicted that Sunday's race would be tainted by fraud and intimidation, but the government declared it "a success."
Egypt's official MENA news service reported that 6,000 members of 76 civil groups monitored the elections. The country rejected international monitoring of the vote as interference in its internal affairs.
Egyptian election commission spokesman Sameh al-Kashef said Tuesday that, although the committee had received numerous complaints, irregularities did not affect the results of the election.
The complaints included reports of riots, fraud and forgery, denying citizens their right to vote, and difficulties faced by the media. There were riots in 16 constituencies, he said.
He said voter turnout was 35 percent.
Various opposition groups have accused the ruling National Democratic Party of using its power to suppress voices critical of Mubarak's nearly three-decade rule. The ruling party has dismissed the accusations.
CNN's Ben Wedeman contributed to this report.