David Cameron has been urged to return to core Conservative values as backbenchers warned of despair and disquiet in the party after its dismal performance in the Eastleigh by-election.
Liberal Democrats landed what Nick Clegg said was a "stunning victory" in the vote despite a turbulent week for the party amid allegations it failed to deal with claims of sexual harassment levelled at its former master strategist Lord Rennard.
But it was the surprise second place polled by the UK Independence Party (Ukip) in the contest that heaped humiliation on the Conservatives.
The Prime Minister acknowledged that the result was "disappointing" but dismissed it as a mid-term protest and insisted he would not now lurch to the right. Some of his backbenchers, however, took to the airwaves to call for a change in direction from the top of the party.
Conservative MP Eleanor Laing, who described herself as having been "utterly loyal" during her parliamentary career, said many Tories felt "hurt" by the way they were treated by the leadership. She told Radio 4's The World At One programme: "They're told that they're old-fashioned and they think that they don't matter and that what they stand for, and what they believe in, doesn't matter."
Mike Thornton won the by-election - triggered by the resignation of the Lib Dem's disgraced ex-Cabinet minister Chris Huhne - with 13,342 votes, a majority of 1,771 over Ukip's Diane James, who said beating the Tories was a "humongous" shock which represented a "seismic shift" in UK politics.
Mr Clegg said the message for Lib Dems from the poll was that "we can be in government and still win". He told activists in Eastleigh: "We held our nerve, we stood our ground... we overcame the odds and we won a stunning victory."
Tory Maria Hutchings polled 10,559 votes - more than 1,000 behind Ukip, which snatched huge chunks of the coalition parties' 2010 general election vote share, taking more than 27% of the total.
Ukip leader Nigel Farage described the result as a "massive boost" and claimed Ukip would cause "an earthquake" in British politics. "People will say it was a protest vote, but who we attracted here were non-voters who had not voted for 20 years - they are not protest votes," he said.
The Hampshire seat is one of a list of 20 Lib Dem-held constituencies Tories believe are crucial for the party to win in 2015 to secure an outright majority. Bob Woollard, chairman of Conservative Grassroots, which was created on the back of opposition to the Government's plans for gay marriage, said the party must return to "core Conservative values" to stand a chance of winning in 2015.