An independent inquiry into why polls for the General Election were so wrong is to take place following yesterday’s shock majority win for the Conservatives.
In the days and weeks leading up to the vote, virtually every major national poll predicted that it would be down to the wire between the Tories and Labour.
Much political campaigning focused on the possibility of a deal with the SNP in the belief that no majority would be reached, necessitating a coalition.
But Britain was stunned yesterday when David Cameron found himself with a slender majority after winning 331 seats (around 37% of the vote), compared with Labour’s 232, vastly defying polling predictions.
The BBC’s David Cowling suggested there were a number of potential reasons for missing a late shift to the Tories.
Virtually every major poll got yesterday's General Election result wrong
He said: “How did all this happen? Shy Conservatives? But why should Conservative voters be alone in being reluctant to declare themselves?
“Where was the Labour zeitgeist in this campaign that made their voters more likely to boast their affiliations?
“Why would Lib Dem voters be less reluctant to proclaim their party allegiance than Conservatives?
“And given the assault on UKIP from every quarter, why would their voters not be the most shy of all?”
Sky News’ Technology Correspondent Tom Cheshire also warned that opinion polls are “not forecasts, but samples”.
He said: “In defence of opinion polls, they are not forecasts, but samples. They usually poll around 1,000 to 2,000 people, over the phone or the internet.
“The exit poll is much more exhaustive, asking 22,000 people how they voted after the fact in 133 constituencies around the country.
Britain was surprised to see David Cameron return to Downing Street so quickly
“That gives a much better idea of the seats a party will win, rather than the brute share of the vote.”
He added: “Getting the poll sample right is becoming harder. Fewer people can be reached by landline telephone these days, and mobiles are less reliable. Internet-based surveys are also being used more and more, but the people who answer them tend to be more self-selecting. “
No definitive answers to why the pollsters did not get it right have been reached and so a new investigation into the errors has begun.
The British Polling Council (BPC) has already launched the inquiry looking at the causes of “apparent bias” and making recommendations for future polls.
The body said in a statement: "The final opinion polls before the election were clearly not as accurate as we would like, and the fact that all the pollsters underestimated the Conservative lead over Labour suggests that the methods that were used should be subject to careful, independent investigation.
"The British Polling Council, supported by the Market Research Society, is therefore setting up an independent inquiry to look into the possible causes of this apparent bias, and to make recommendations for future polling.
"We are pleased to announce that Professor Patrick Sturgis, who is professor of research methodology and director of the ESRC National Centre for Research Methods, has agreed to chair the inquiry, and will take the lead in setting its terms of reference.
"The membership of the inquiry will be announced in due course."
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Interestingly, Survation said it conducted a telephone poll on Wednesday evening which showed the Tories on 37% and Labour on 31% but "chickened out" of publishing it as it appeared so out of line with all the others.
Its chief executive Damian Lyons said he would "always regret" the decision but would not be carrying out an internal review of his methodology.
Addressing the unpublished poll, Mr Lyons said: "We had flagged that we were conducting this poll to the Daily Mirror as something we might share as an interesting check on our online vs our telephone methodology, but the results seemed so out of line with all the polling conducted by ourselves and our peers - what poll commentators would term an outlier - that I chickened out of publishing the figures - something I'm sure I'll always regret."
ICM director Martin Boon appeared to sum up the mood among Britain's pollsters, tweeting "oh shit" after the publication of the exit poll showing the Tories would be by far the largest party.
YouGov chief executive Stephan Shakespeare tweeted: "A terrible night for us pollsters. I apologise for a poor performance. We need to find out why."
Andrew Cooper, of Populus, welcomed the investigation and said: "There are likely to be a variety of reasons behind the difference in the polls and the final outcome. Very late swing to the Conservatives, polling weightings, polling methodology and claimed propensity to vote will be just some of the factors that are likely to be discovered once an investigation is completed."
ComRes chairman Andrew Hawkins said "there was no need to throw the baby out with the bathwater" and said his organisation did not offer a seat prediction but instead a snapshot of voting intention.
Mr Hawkins also pointed out that the Tories had been leading its polls all year and ComRes published an article in April urging voters to "look past the poll of polls".
He said: "Some commentators have been very quick to put the boot into pollsters for calling it wrong.
"The truth is that pollsters, when they stick to their knitting, measure vote share.
"We do indeed, together with academics and the media, need to look at how that vote share translates into House of Commons seats - that is certainly true.
"But there is no need to throw the baby out with the bathwater. Most of the polls from most of the pollsters were within the margin of error.
"How they are interpreted and reported needs to be a matter of collective consideration."
Pollsters were slated by Labour’s election strategist David Axelrod, who described the errors as a “stark failure”.
The BBC's Robert Peston also described the issue as "unsettling".
