Mr Nour's party has accused the NDP of intimidation and vote-buying
Egyptian opposition leader Ayman Nour lost his parliamentary seat in Wednesday's first-round election, Egypt's election commission has said.
The leader of the al-Ghad Party was beaten by the ruling National Democratic Party (NDP) in the central Cairo district of Bab al-Sharia.
Mr Nour says voting there was marred by fraud and intimidation.
Preliminary results suggest that the NDP will retain its control of the People's Assembly.
Intisar Nasim, assistant justice minister and secretary general of the higher parliamentary election commission, told Egyptian television that half the results were now known.
On Wednesday, voters in eight governorates chose between some 1,500 candidates competing for about 180 of the 444 elected seats in the People's Assembly.
Egyptians in the remaining 18 governorates will vote on 20 November and 1 December, with the final outcome of the election not likely to be known until the middle of December.
Mr Nour lost his seat of 10 years to the NDP's Yahya Wahdan, a former security officer.
Despite Mr Nour's popularity as one of Egypt's leading pro-democracy figures, it was always expected he would lose his seat given the ferocity of the NDP campaign against him, says the BBC's correspondent in Cairo, Heba Saleh.
However, Mr Nour disputes the result and has accused the NDP of intimidation and vote-buying in the constituency.
"What happened today is not an election," Mr Nour told the Associated Press on Wednesday.
Mr Nour gained prominence when he formed the al-Ghad Party in October 2004.
It soon became the largest opposition party in the People's Assembly, with six deputies.
Three months later Mr Nour was charged with forging documents in his party's application papers.
The case came to court in June, but was postponed allow him to stand in September's presidential election.
Having come second to President Hosni Mubarak in the poll, he will have to return to court on 26 November. Mr Nour denies the charges.
NDP leaders safe
The election was not expected to challenge the National Democratic Party's dominance of the People's Assembly and preliminary results appear to confirm such predictions.
Senior NDP leaders and government ministers standing in the eight governorates contested yesterday retained their sears.Fathi Surour, the speaker of the People's Assembly, and Zakaria Azmi, the chief of the presidential cabinet, were re-elected in Cairo, while NDP vice chairman Kamal al-Shazli won in the Nile Delta.