Exit poll results: Conservatives 10 short of a majority in shock prediction, but how much should we trust it and will it be right?

Exit polls have been very accurate in the past but with the surge of the SNP and Ukip, it makes it much tougher for pollsters to predict a national result at 10pm

The exit poll has predicted the Conservatives are on course to win 316 seats - just 10 short of a majority, but a final YouGov prediction shows a much closer result.

Should we trust the exit poll? In some ways it is the most accurate of all the polls before the final result is announced early on Friday morning, because it tells us how people have voted rather than how they will vote.

However considering it is so different from most pre-election polls, many are questioning its accuracy and YouGov said it found no reason to change its final prediction before polling day, which put the Tories on 284, Labour on 263, Lib Dems on 31 and the SNP on 48.

Lord Ashcroft meanwhile has also put the result much closer, with his post-vote poll of a sample of 12,000 putting the Conservatives on 34 per cent and Labour on 31 per cent.

So how does the exit poll work? This year it is conducted jointly for the BBC, ITN and Sky and uses surveys of roughly 20,000 people to tell us how the nation has voted.

It is conducted by 140 researchers at 140 polling stations across the UK, with venues chosen that are seen to be representative of the constituency they are in.

In 2010 the exit poll was very accurate, under-predicting Labour’s seat share by three and over-predicting the Liberal Democrats by two.

But in 1992 the two exit polls for ITN and BBC wrongly predicted a hung Parliament - John Major had just about secured a majority for the Conservatives.

It could have been even worse for the BBC, had it not made a last-minute adjustment before David Dimbleby addressed the nation. Minutes before 10pm it was predicting a Labour majority.

This election could see a repeat of 1992 as the rise of smaller parties make it much more complicated to predict how some of the most marginal constituencies will swing.

Stay up to date with all the latest election developments as the results roll in with our live-blog.

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