The Conservative party has won the Norwich North by-election, overturning the 5,459 Labour majority won by Ian Gibson at the 2005 general election.
Tory candidate Chloe Smith took the seat with 13,591 votes - a majority of 7,348 - just over double Labour's 6,243 votes.
The victory represents a 16.49 per cent swing to the Conservatives.
But Labour, resigned to defeat at the poll, will be relieved to cling on to second place ahead of the Liberal Democrats.
The by-election was the first Westminster election since the expenses scandal hit the Commons, and was predicted to be a must-win for David Cameron's Conservatives.
The Conservative leader visited the constituency six times during the campaign.
Gibson quit Parliament after being banned from standing at the next general election by the Labour National Executive Committee over his expenses claims.
He chose to stand down immediately rather than serve out the rest of his term in the Commons.
The Daily Telegraph revealed that he had claimed almost £80,000 on parliamentary expenses to pay for his daughter's home, before selling it on to her for half its market value.
Speaking after her victory Smith paid tribute to her predecessor:
"In Ian Gibson, the people of Norwich North had an MP who was a strong, independent and local voice.
"I am determined to represent the people of Norwich North with the same honesty and conviction," she added.
Smith said her election represented a victory for "honest politics" and that people had not just voted against Labour Party, but had voted for the Conservatives.
At 27, Smith will become the youngest MP at Westminster, a distinction previously held by 29-year-old Liberal Democrat Jo Swinson.
The Labour campaign also ran into trouble when their candidate Chris Ostrowski was forced off the campaign trail after contracting swine-flu and being admitted to hospital.
Turnout was around 45 per cent, down on the 61.09 per cent at the 2005 general election.
The Green Party also failed to meet expectations, falling to fifth place, beaten by the UK Independence Party.
UKIP came a strong second in the East of England region at the recent European parliamentary elections, while the Greens won more votes than any other party in the Norwich City Council area at the same poll.
Twelve candidates stood in total, including the British National Party, the Libertarian Party, and independent Craig Murray, the UK's former ambassador to Uzbekistan.
The Norwich North by-election results in full:
Chloe Smith (Conservative) 13,591
Chris Ostrowski (Labour) 6,243
April Pond (Liberal Democrat) 4,803
Glenn Tingle (UK Independence Party) 4,068
Rupert Read (Green) 3,350
Craig Murray (Put An Honest Man into Parliament) 953
Robert West (British National Party) 941
Bill Holden (Independent) 166
Laud Howling (The Official Monster Raving Loony Party) 144
Anne Fryatt (None of The Above Party) 59
Thomas Burridge (Libertarian Party) 36
Peter Baggs (Independent) 23
