British Prime Minister David Cameron is under pressure after his Conservatives were beaten into third place in a key by-election by his scandal-hit coalition partners and a eurosceptic party.
Cameron admitted it was a "disappointing" night for his party after the Liberal Democrats held the parliamentary seat of Eastleigh in southern England in a contest billed as the most important British by-election in a generation.
The Conservatives had hoped at least to come in second but were condemned to third by the anti-European Union and anti-immigration UK Independence Party, which registered its best ever performance in a parliamentary election.
The vote was sparked by the resignation of former energy minister Chris Huhne, a Liberal Democrat who has pleaded guilty to trying to avoid a speeding fine.
Deputy Prime Minister Nick Clegg, whose own position as Lib Dem leader had been on the line after a collapse in the party's poll ratings, said the "stunning victory" showed they "can be a party of government and still win".
UKIP leader Nigel Farage meanwhile insisted the party's best ever result in a British election was not a "protest vote".
Cameron said he was "confident" the Conservatives could win back support at the next general election, due in 2015, and rejected suggestions that the party would lurch to the right in response.
"It is a disappointing result for the Conservative party but it's clear that in mid-term by-elections, people want to register a protest," he said.
Lib Dem candidate Mike Thornton secured 13,342 votes, 1771 more than UKIP representative Diane James.
Tory nominee Maria Hutchings limped in third with 10,559 votes in a seat that the Conservatives held as recently as 1994, while the main opposition Labour party's candidate John O'Farrell was fourth with 4088.