The Liberal Democrats have dismissed exit poll suggestions that the party could be reduced to a rump of just 10 MPs.
The loss of dozens of Commons seats would heap pressure on Nick Clegg’s leadership but party sources insisted the projection did not correspond with the data they had gathered on the ground.
Mr Clegg’s party won 57 seats in 2010 and Lib Dem sources have suggested they “realistically” expected to return 30 or more MPs despite stubbornly low opinion poll ratings.
On the eve of the election Mr Clegg insisted his party would be the “surprise story” of polling day, defying predictions of an electoral mauling.
Responding to the joint BBC/ITN/SKY exit poll, a Lib Dem spokesman acknowledged the election was “unpredictable” but rejected the findings.
A party spokesman said: “This exit poll does not reflect any of our intelligence from today or in the run-up to polling day. We will wait for the final results.”
The spokesman added: “No opinion poll to date has shown the numbers in this exit poll.”
The poll put Conservatives on 316 – just 10 short of the magic number of 326 needed to command an absolute majority in the House of Commons. Labour were forecast to secure just 239 – 17 fewer than their tally at the start of the election campaign – with the Scottish National Party almost achieving a clean sweep of 58 of the 59 seats north of the border.
Mr Clegg has insisted he is “confident but not complacent” about holding on to his own seat in Sheffield Hallam despite a Labour campaign to unseat him, with a seven point lead in the latest constituency opinion poll.
But the exit result would appear to confirm that key allies, including Cabinet minister Danny Alexander, face defeat as voters turn away from the party over its role in the coalition Government.
In Scotland, where Mr Alexander and his allies attempt to hold off the SNP surge, the Lib Dems hope tactical voting against the nationalists will help save some of their 11 seats.
In south west England, the main contest faced by Mr Clegg’s party is from the Tories, and David Cameron has targeted the area as part of his plan to win an outright majority.
Elsewhere, the backlash over the party’s U-turn over tuition fees looks set to cost it dear in areas where there is a large student vote.
Mr Clegg has insisted that national opinion polls, which have been stuck stubbornly at around 8%, do not reflect the picture in battleground seats where the party is able to mount a ground campaign with activists out on the doorsteps.
He said: “At the beginning of this campaign we were written off and yet … when the polls close, the Liberal Democrats will be the surprise story of this General Election campaign because we are going to win.”