David Cameron will fall 19 seats short of a Commons majority, according to a joint BBC/Sky/ITV exit poll.
The Conservatives would have 307 MPs, up 97 on 2005, Labour would have 255, down 94, and the Lib Dems 59, down 4. Nationalists and others would have 29.
That means Labour and the Lib Dems together could not have a majority.
There are reports of long queues of people still waiting to vote in some parts of the country after the most closely fought election in decades.
Conservative leader David Cameron might find that winning one or two seats in Northern Ireland and forming a deal with the Democratic Unionist Party might be enough to give him a majority, making him Britain's next prime minister.
The exit poll anticipates that the Labour Party has been more successful at holding on to its vote in seats in Scotland and Wales in seats where there is a large ethnic minority population and where there is an incumbent Labour MP standing again.
The poll also anticipates the Lib Dems will perform better in England than in either Scotland or Wales, but a fall in number of MPs would still come as a blow to Lib Dem leader Nick Clegg, who has been neck-and-neck in the polls with the other two main parties for much of the campaign.
I THINK CAMERON WILL BE ASKED TO LEAD A NEW GOVERNMENT AND HE WILL DO IT.
ONE SEAT DECLARED: FOR LABOUR - BUT THEIR VOTE IS DOWN 12% AND THE TORIES' UP 5%. THIS WOULD TRANSLATE INTO 342 SEATS FOR THE TORIES AND AN OUTRIGHT MAJORITY.
2ND SEAT DECLARED: ANOTHER LABOUR HOLD, BUT AGAIN: CONSERVATIVES PICK UP 12%...
IF THIS HOLDS UP, THEN THERE'LL BE A 342 MAJORITY FOR THE TORIES...
UPDATE: A 20% SWING TOWARD THE TORIES... TORIES UP 6% LABOUR DOWN 14%... STAY TUNED...
3RD SEAT: A LABOUR HOLD, BUT THE SWING TOWARD THE TORIES REMAINS THE SAME... A GOOD OMEN...
8PM UPDATE: HUGE TAKE-AWAY FOR THE TORIES - IN KINGSWOOD - IT MEANS THAT THE TORIES CAN WIN A MAJORITY...
IT LOOKS LIKE THE TORIES WILL WIN BASILDON TOO - ANTOEHR BELLWEATHER RESULT!
BIG SWINGS TO THE TORIES - MORE THAN THEY NEED!
UPDATE: 8:42PM: GUARDIAN:
Guardian psephologist Lewis Baston says he thinks the Tories are on course for an outright majority.9:29 PM: TORIES ARE DOING WELL IN WALES - MAKES SOME PICKUPS. OTHER GOOD PICKUPS.
BIG STORY: LIB-DEMS DOING NOTHING.
AND: THE SWING FROM LEFT TO RIGHT ISN'T CONSISTENT - NOT BY REGION OR CONTEST. THEREFORE, THE RACE WON'T BE DECIDED UNTIL THE MORNING AND THE LAST FEW SEATS ARE DECIDED.
10:33 PM: THIS JUST IN FORM THE BBC-TV: BILL WYMAN OF THE STONES WANTS THE TORIES TO WIN!