A lone protester attempted to pelt newly elected MP George Galloway with eggs as he celebrated his by-election victory.
Thomas Johnson, 26, of Bradford, West Yorkshire, called Mr Galloway a "parasite" as he threw the eggs towards him.
The attack happened as the MP left his party's West Bradford headquarters and prepared to board his open-top bus for a tour of the city.
Mr Galloway was not hit but eggs exploded on to the windows of the Chambers Solicitors office, where the campaign was based, and showered those standing below with yolks, egg whites and fragments of shell.
Mr Johnson shouted: "He's a sycophant, he's a greedy leech, he's a parasite on this city."
The Labour leader Ed Miliband said he is "incredibly disappointed" by the by-election results in Bradford West and said he would visit the constituency to "talk to people there about why this result happened".
He said: “Clearly there were local factors, but I also say only four out of 10 people voted for the three mainstream political parties. We've got to understand the reasons why that happened in Bradford."
The deputy Labour leader Harriet Harman told ITV News that George Galloway's victory shows there is "a particular issue about that local community and the Labour party" and that there is not a "general issue" with Labour's electability.
Toby Perkins, Labour MP for Chesterfield, told ITV Calendar that the Bradford West constituency has always bucked the national trend. He conceded that the Respect party campaign gathered considerable momentum but said that two weeks earlier Labour could have won "by 11 or 12 thousand votes".