The Conservatives have won the Norwich North by-election with a majority of 7,348, inflicting a damaging defeat on Labour.
Labour, which had held the seat comfortably since 1997, saw its majority of 5,459 easily overturned by the Conservative candidate Chloe Smith. Smith, 27, will become the House of Commons' youngest MP when she takes her seat in the autumn.
The by-election was was triggered by the resignation of Ian Gibson, who decided to step down after Labour's 'star chamber' banned him from re-election following revelations that he claimed almost £80,000 in expenses on a flat which he later sold at a discount to his daughter.
Turnout was 45.88 per cent-significantly lower than the 2005 figure of 61.09 per cent, as many regular voters stayed at home in the first by-election since the expenses scandal.
Labour's high command will now begin an inquest into the party's defeat, with a number of MPs arguing that the decision to ban Gibson backfired. A significant number of voters reportedly refused to back the Labour candidate, Chris Ostrowski, because they were unhappy over the treatment of Gibson.
In her acceptance speech Smith paid tribute to Gibson, describing him as a "strong, independent and local voice".
Speaking earlier, Ben Bradshaw, the Culture Secretary, conceded that the result had been disappointing for Labour but added that it was not as bad as last year's by-election results.
"It's a very disappointing result, we had a great candidate. This was always going to be a difficult by-election," he told Sky News.
"I haven't had the chance to analyse the figures, but it wouldn't appear to be as bad as the by-elections we lost last year."
He also admitted that the expulsion of Gibson appeared to have contributed to Labour's defeat.
The full results were:
Chloe Smith (Conservative) 13,591
Chris Ostrowski (Labour) 6,243
April Pond (Liberal Democrat) 4,803
Rupert Read (Green) 3,350
Robert West (BNP) 941
Craig Murray (Put an Honest Man into Parliament) 953
Peter Baggs (Independent) 23
Bill Holden (Independent) 166
Thomas Burridge (Libertarian) 36
Howling Laud (Monster Raving Loony) 144
Anne Fryatt (NOTA) 59
Glenn Tingle (UK Independence Party) 4,068