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Liberal Democrat leader Nick Clegg says Conservatives should get first chance to form government.
Conservative Michael Gove says the swing towards his party in terms of seats gained is bigger than that achieved under Margaret Thatcher in 1979.
Lib Dems: 50
Gordon Brown will only resign if he cannot get a majority in the House of Commons, the BBC reports.
Only in the event that he fails to reach a deal with the other parties can David Cameron have a go at forming a government.
But political editor Nick Robinson says his instinct is that Cameron will become the next Prime Minister.
Nick Clegg has made his acceptance speech after retaining the seat of Sheffield Hallam while acknowledging defeat on behalf of the party.
"This has obviously been a disappointing night for the Liberal Democrats. I think we engaged a lot of people in the campaign even if they didn't go on to vote for the Liberal Democrats.
"As for what happens next ... No one appears to have won emphatically."
The Press Association reports voter turnout is hovering in the mid-60s - recently at 64.6 per cent.
The latest poll count puts the Conservatives ahead on 274, with Labour at 226 and the Lib Dems at 47.
With 530 of the 650 seats having reported, Labour cannot now win enough seats to command an overall parliamentary majority.
Liberal Democrats: 40
Exit polls suggest no party will win a majority - the Conservatives are forecast to win 305 seats, Labour 255, and the Liberal Democrats 61.
326 are needed for a majority.
However, Gordon Brown has pointed out that the (unwritten) constitution gives the sitting prime minister the right to try to form a government first.
tweets: "Reporters to [Vince] Cable: 'What happened to Cleggmania?' Cable: 'There's not a lot of it around'. Zac Goldsmith's win confirms it."
Cable has just been re-elected in Twickenham.
Meanwhile, Labour have managed to stave off the BNP in Barking.
The first Green MP has been elected, according to the
The Greens took Brighton Pavilion from Labour, a breakthrough for the party after intensive campaigning by leader Caroline Lucas.
"Tonight the people of Brighton Pavilion have made history by electing Britain's first Green MP," Lucas told Reuters. "Thank you so much for putting the politics of hope above the politics of fear."
has rounded up a list of significant election seat losses, including science commentator Dr Evan Harris, former Labour Home Secretaries Jacqui Smith and Charles Clark, and Lembit Opik, who regularly makes appearances on various TV shows.
Over two-thirds of the 650 seats have been counted.
With 491 of 650 seats called, the Tories have 240 (gained 69), Labour 187 (lost 63) and the Lib Dems 38 seats (lost 5).
Votes: 8,108,149 for the Tories, 6,239,970 for Labour and 4,995,273 for the Lib Dems.
Lord Ashcroft has spoken out on the election, telling the BBC that the televised debates were to blame for the Conservative Party's downfall.
"The debates .. turned everything topsy turvy. This is the sort of result that we're now seeing as a result of those debates."
Asked if the Tories regretted taking part in the debates, he replied: "It's a balanced argument - it brought greater awareness of politics - greater turnout, greater discussion - but with a pure strategic, hindsight view you'd much prefer the Tories going into today 10 points ahead rather than 3 or 4 points ahead."
Latest vote counts, with 414 of 649 seats counted and one further seat to be decided on May 27:
Lib Dems: 28
writes that the Lib Dems failed to live up to hype and the Conservatives failed to make what should have been easy gains.
"It looks like we the people have turned out in record numbers to punish the major parties equally. And, judging from Scotland, the minority parties too. Fun for the time being but this is going to spell mayhem over the coming days."
Former Home Secretary David Blunkett says Labour must now move to form a coalition if possible.
Mr Blunkett told BBC News: "My instinct is that regrettably we have lost the election. We should now go for uniting the anti-Conservative forces, if we are in a position, in a way that minimises the damage they can do to the economy, social policy and the wellbeing of the people who voted for us in the election yesterday."
says the Birmingham Edgbaston count is rapidly becoming a "farce".
"Three hours late, with three recounts, all of which showed Labour winning by 1,300 votes, many Conservatives are privately embarrassed by their party's contesting of the result.
, 'I don't know what we're doing - it's not like they're going to find a thousand votes hiding in a bundle under the table'."
highlights one of the night's firsts: "At a stroke, Britain now has its first two Asian female MPs."
Halfway through vote counting, the Conservatives have done better than exit poll predictions while Labour and the Liberal Democrats are behind expectations.
It has been more than six hours since polls closed.
After 325 of 650 seats:
Conservatives: 156 (3.5 seats ahead of exit poll predictions)
Labour: 122 (5.5 seats behind)
Liberal Democrats: 23 (7.5 seats behind)
The Lib Dems and Labour are already negotiating a coalition but they might not reach a majority even combined, the BBC says.
Approaching 4am UK time, less than half of constituencies have been called. Results so far put the Conservatives clearly ahead but projected to get less than half the seats.
"We've got a real cliffhanger on our hands," said Professor John Curtice, an analyst for the BBC.
A Tory majority seems unlikely - but a Labour-Lib Dems coalition may similarly not have enough, he said.
said it was "still unsure what to do with tomorrow's front cover".
"However frustrating it is at this time of the morning we still do not have a clear picture," said Labour's Alistair Darling.
Labour: 113 (lost 28)
Conservatives: 131 (gained 30)
Lib Dems: 21 (lost 2)
Prime Minister Gordon Brown has indicated he might attempt to form a coalition government.
Speaking in his home district in Scotland, Brown vowed to "play my part in Britain having a strong, stable and principled government" - the clearest sign yet that he would try to cling to power and seek an alliance with the third-place Liberal Democrats.
Brown also pledged action on election reform - a key demand of his would-be partners.
Meanwhile, opposition leader David Cameron said Labour had lost its mandate to rule.
"I believe it is already clear that the Labour government has lost its mandate to govern our country," he said after winning his rural constituency.
The Conservatives and Labour are tied in seats won at 76 each as Conservative leader David Cameron gave a speech after winning his constituency.
Cameron pushed a narrative being put forward by the Tories all night that Labour has lost its mandate even if there is a hung parliament.
"Nationally we have to wait ... but I believe the Labour Party has lost its mandate," Cameron said.
His constituency was full of colourful candidates - including a stout man running for the Monster Raving Looney Party and a man wearing a dirty white robe.
The Conservatives have won the recounted Broxtowe by a tiny 389 votes.
Meanwhile, there is excitement in another key contested electorate, where a partial recount was called two hours after results were expected.
The Labour candidate at Birmingham Edgbaston gave her staff high-fives, the BBC reported, saying the Conservatives will be "very disappointed" if they don't come out ahead.
Lib Dems: 9
One in five seats have been called and Labour have lost 12 seats while the Conservatives have gained 12 - but the BBC emphasises that "there is no clear picture yet".
The Liberal Democrats have not gained any seats - instead, they have lost one. This is bad news not just for the Lib Dems but for Gordon Brown and Labour, for whom holding on to power depended on a coalition with a strong Lib Dem Party.
After 130 of 650 results:
Lib Dems: 7
Bond markets opened at 1.30am UK time, with prices rising as dealers anticipate a victory for the Conservatives.
says a "prediction market" trading on anticipated election results is moving away from an outright Tory victory - predictions have halved to 37 per cent in half an hour.
"The Conservatives are doing well in seats where the Lib Dems threatened them, but not so well in seats they hoped to win from Labour."
A recount has been ordered in one electorate - Broxtowe - because votes are too close to call.
The BBC has called it a "mysterious" election with no one sure where the results will end up.
A tenth of the seats have been called with Labour having lost two seats and the Conservatives gaining two.
Swings from Labour to the Tories in key electorates have ranged widely, from up to 9 per cent down to 3 per cent - not enough for the Tories to win an outright majority.
The Liberal Democrats, meanwhile, have so far failed to gain traction.
says: "The big story of the night may well be the stunning failure of the Lib Dems."
After 65 of 650 seats:
Lib Dems: 4
reports: "Ed Miliband, the Energy and Climate Change Secretary, says it all, after a baffling series of results. 'The people have spoken, and we don't know what they have said.'"
Gordon Brown has held on to his seat, but results so far suggest a significant swing to the Tories with some now suggesting they may win an outright majority.
On Twitter: "This is DEFINITELY a farewell speech from Gordon Brown."
"Sounds more like a resignation speech."
"Gordon Brown looks pretty shattered."
Students claim they were discriminated against and shut out of elections in favour of "local residents" and have set up a
It identifies itself as:
"Anyone who started queuing after 5.30 (correct me if it also affected people who started queuing before this point) who were discriminated against in the speed of which they were able to vote because of the creation of a separate faster queue for local 'residents'."
Amy Mallett - So they go on about students being apathetic and not using our vote..... then when students try to vote they actually stop us? Can someone explain the logic to me please?
Jonathan Wright - Hundreds of students were discriminated against today as 'local residents' were allowed to skip the queue of students wanting to vote. I was at the front of the queue when this decision was taken at approximately 7.30 and challenged it at the time with the person In charge and... also called a helpline number NO action was taken to stop this at the time. I was stood near the front of the queue for approximately 30 minutes whilst ALL the people allowed to vote were non students who had been allowed to skip the queue.
A few more results have come in, with Labour taking two more, the Liberal Democrats its first, and three minor parties winning a seat each.
Total so far:
Lib Dems: 1
Exit polls show the Conservatives capturing the largest number of seats but failing to secure a majority, according to television projections.
An analysis by Britain's main television networks suggested David Cameron's Conservative party will win 305 House of Commons seats, short of the 326 seats needed for a majority.
The projections also showed a substantial drop for Prime Minister Gordon Brown's ruling party, giving it 255 seats - its smallest number since 1987.
Counting in a Northern Ireland electorate had to be suspended because of a bomb alert, reports the
A car, hijacked earlier in the city, was abandoned in a car park outside a polling centre.
Counting was stopped while a controlled explosion was carried out to defuse the bomb, the BBC says.
Police say it was a legitimate bomb scare - there was a viable explosive device in a car left near the centre, from where 500 people were evacuated.
jokes that Britain can learn from New Zealand, saying "yes, really".
From the markets: a Conservative lead in exit polls pushes the pound up (the
), but the possibility of a hung Parliament would get a "very dismal" reaction from markets (the
Meanwhile, Twitter responds to the BBC's comparisons of the Queen to a Heineken lager and when she will be "activated".
"The Queen is like Heineken lager - she reaches parts of the constitution only she can reach .... Classic."
"BBC1 'The Queen is like Heineken Lager' What?!"
"Aaargh, there's a man on BBC1 talking about 'When the Queen is activated.' I'm frightened. Hold me."
says there are sit-ins in Britain preventing ballots from reaching counting centres, as a protest against people being shut out of voting booths.
"There are reports of sit-ins in Hackney, protests in Manchester and more protesters preventing ballot boxes from reaching the counting centre in Sheffield.
"All are protesting over being unable to vote because of queues when polling stations closed at 10pm."
Results of the UK election may be open to legal challenge if they end up close, with people queuing around the block outside closed election stations.
The BBC calls it an "increasing scandal" - some polling booths ran out of voting papers and others kept taking votes after exit polls closed.
comments: "The view from Zimbabwe: when I covered the 2005 presidential elections there, voters who were in the queue when polling stations were supposed to close were allowed eventually to vote. In Britain, apparently, if you weren't through the doors by 10pm, you don't get to vote. Which one is the more democratic?"
Summary so far:
Labour: 3 seats
Liberal Democrats: 0
Exit polls point to a hung Parliament with Conservatives having the most seats but not a majority.
Labour takes another seat in an electorate where the Conservatives were thought to have had a chance to win.
Labour holds Sunderland Central with just a 4.8 per cent swing to the Conservatives, much less than the first two.
The Conservatives needed a 12.8 per cent swing to win the seat.
On Twitter, reaction to exit polls is placing Labour firmly in second and the Lib Dems hardly gaining seats despite an expected surge in votes nationally: Gordon Brown now favours the Second Past the Post system.
The swing to the Conservatives in counted votes has been pushed to more than 10 per cent despite Labour winning the second seat. If this keeps up, it would be the biggest swing since World War II, says the BBC.
Sunderland West goes to Labour with 19,615 seats, compared with 8157 for the Conservatives.
Seats counted so far:
Lib Dems: 0
Heavy turnout is being blamed for delays in polling results.
With no clear winner in the exit polls, on Twitter: "Fox News just called the UK election for Bush."
Prof Vernon Bogdanor, from Oxford University, tells the BBC that if the swing of 8.4 per cent in Houghton and Sunderland South is repeated across the country there will not be a hung parliament - the Conservatives will have an outright victory.
two seats have been given to Lib Dems from the Conservatives. Not a significant change.
The BBC reports polling stations were the busiest in memory, with many voters unable to get in by the 10pm (UK time) deadline.
"It's a disgrace, isn't it. It really is a disgrace," a correspondent said.
"We were told by the polling officer at our station in North London that it was the busiest polling day he could remember - and he's been doing it for 25 years. He said it was absolutely rammed in the first two hours."
The first election results are in: Labour has retained its seat in the Sunderland South electorate, in northeast England. Labour's Bridget Philipson - who is just 26 - is the only MP elected so far.
reports the results from Sunderland South supports exit poll results: a small swing from Labour to Conservatives, and a small drop for the Lib Dems.
reports that California Governor Arnold Schwarzenegger has called Tory leader David Cameron to congratulate him on victory.
reports police have had to quell upset voters who were cut off while waiting in queues.
"Police officers at a polling station in Brockley in Lewisham, south-east London, tell a BBC camera crew that voters are still being allowed to vote at 10.30pm. But the returning officer for Sheffield is apologising after people were unable to cast their votes there because of huge queues at polling stations. John Mothersole admits they were caught out."
British commentators discuss the exit polls as they await results from the first electorates.
questions exit polls showing the third party, the Lib Dems, losing seats despite earlier polls suggesting major gains on the back of its party leader, Nick Clegg, who performed well in the country's first televised debates this year.
"At first glance the exit polls look implausible when it comes to the Lib Dems, even with 18,000 people questioned. After the Clegg Bounce and, apparently, a rather enthusiastic turnout today, is it likely they would lose seats? I doubt it for now."
Television projections based on exit polls suggest the Conservatives have won the largest number of seats in Britain's national election, but will fall slightly short of a majority.
A BBC analysis suggested David Cameron's party will win 307 House of Commons seats, short of the 326 seats needed for a majority, according to results from the poll for three broadcast networks.
Two scenarios could arise - Prime Minister Gordon Brown could resign if he feels the results have signalled he has lost his mandate to rule, or he could try to stay on as leader and seek a deal in which smaller parties would support him.
- NZHERALD STAFF