Theresa May has suffered a heavy blow after the official exit poll indicated Britain is heading for a hung parliament.
The survey of some 20,000 people leaving polling stations suggested Ms May's party has taken just 314 seats in total, 12 short of an overall majority.
The unexpected result would see Labour increase its number of seats by 34 to 266, while the Liberal Democrats would take 14. Nicola Sturgeon's SNP appear to have suffered heavy losses.
If borne out, the figures would throw a huge question mark over Ms May's future as Prime Minister – with Labour figures already demanding her resignation.
But the result threatened to throw Britain's Brexit negotiating strategy into chaos, with talks due to begin in just 11 days and British parties bitterly divided over what to do.
In an early sign of repercussions the result would have, sterling fell over 1.5 per cent to £1.27 and plummeted over one per cent to €1.13.
Conservatives attempted to play down the poll, with Defence Secretary Michael Fallon saying it was just a "projection".
He went on: "These exit polls have been wrong in the past. I think we do need to see some actual results before this can be interpreted one way or another.
"I never believed the original poll showing us 20 points ahead – in an election you get a tightening between the major parties, that was clearly happening this time."
Despite a faltering campaign, punctuated by a humiliating U-turn over social care, most Conservatives still believed their party was on course for a decent majority, bigger than the one David Cameron secured in 2015.
The poll leaves the Conservatives with 17 fewer seats than they currently have, while Labour appears to have won 34 more seats than the party did under Ed Miliband two years ago.
Shadow Chancellor John McDonnell said if the poll is right, it would "change the nature of political discourse in this country".
"I think people have got tired of the ya-boo politics and some of the nasty tactics that have some out in recent years," he said.
Describing the Tory campaign as "gutter", he added: "If the result is anywhere near like this I think it means positive politics has actually succeeded."
Mr Corbyn's less polished, more open campaign contrasted well with Ms May's, but a string of opinion polls still predicted a Tory majority.
Both Mr McDonnell and shadow Foreign Secretary Emily Thornberry suggested Ms May could no longer continue as Prime Minister, if her gamble falls through.
Another key feature of the exit poll is the reduction in seats for the SNP, with the party taking 34 after having won 56 in 2015.
With Lib Dem leader Tim Farron almost doubling his party's tally to 14, enough to provide a majority with the Conservatives, coalition government could be a possibility – as could a progressive alliance of centre left parties.
But ex-leader Menzies Campbell said Mr Farron had made it clear there would be no pacts and no coalitions.
He went on: "We've had our fingers burned by coalition, I don't need to tell you that, so I find it very difficult to see how Tim Farron would go back on what he has already said and indeed to persuade the membership of the Lib Dems that a coalition was a good idea from our point of view."
The poll indicated the Greens would retain their seat, while Ukip would lose their only place on the Commons benches.
Before the survey was even released Ukip spinners were playing down expectations for the party, suggesting nobody believes party leader Paul Nuttall would emerge victorious in Boston and Skegness – despite the constituency voting heavily to Leave at last year’s referendum.
"In all seriousness it’s not one of our target seats," one Ukip source added.
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