The Conservatives are confident David Cameron will remain PM with early general election results suggesting the party will be close to a majority.
Labour faces being wiped out in Scotland by the SNP and is failing to make the gains it needs in England to stand a chance of forming a government.
The Lib Dems are on course to be decimated with the exit poll predicting they will have just 10 MPs.
The exit poll suggested Labour will get 239 MPs to the Tories' 316.
Results so far suggest it is accurate but the majority of the 650 seats have yet to declare.
If the exit poll is accurate, Mr Cameron will be able to remain in Number 10 as the head of a minority government without the need for a coalition - although he might have to rely on the support of the DUP or the Lib Dems.
Even if Labour leader Ed Miliband was able to persuade the Lib Dems to join the SNP in backing a Labour government, he would not have the necessary numbers to get his legislative programme through Parliament in a Queen's Speech.
The finishing line needed to form an absolute majority is 326, but because Sinn Fein MPs have not taken up seats and the Speaker does not normally vote, the finishing line has, in practice, been 323.
Labour insists Mr Miliband could still be prime minister because the coalition's majority will have disappeared but senior party figures have conceded they are having a disappointing night.
Labour is being hammered in Scotland by the SNP, with Nicola Sturgeon's party predicted to take 58 of the 59 seats.
Jim Murphy, leader of the Scottish Labour Party, and shadow foreign secretary Douglas Alexander have both lost their seats to the SNP, which is benefiting from a 27% average swing from Labour.
Conceding defeat, Mr Murphy said it had "proven hard to turn round years of difficulties with the Scottish Labour Party in just five short months".
He congratulated the SNP on the scale of their victory but said he intended to continue as the party' leader in Scotland.
"Scotland needs a strong Labour Party and our fightback starts tomorrow morning," he added.
Labour has failed to make the headway it wanted in the South of England and the Midlands, failing to take its top target seat, Warwickshire North, back from the Conservatives.
Its progress in London has not been as strong as pre-election polls suggested.
There is a recount in Bradford West, where George Galloway is battling Labour to retain the seat he won in a by-election.
Bradford Council has reported Mr Galloway to the police for allegedly breaking election law for tweeting about exit polls before polls closed, the BBC has learned.
The exit poll suggests the Lib Dems will lose 47 seats, with many of their high profile minister and MPs facing defeat, and the party finishing behind the Greens in early results.
Lib Dem election chief Lord Ashdown told the BBC: "If this exit poll is right I will publicly eat my hat."
(BBC)