Labour election strategist David Axelrod slammed the "stark failure" of Britain's pollsters as they faced up to an independent inquiry into their failure to call the Conservatives' shock election majority.
Axelrod, a highly paid former adviser to United States president Barack Obama, said he had never seen a deficiency in polling like it, with almost all surveys predicting a hung parliament.
His comments came as the British Polling Council (BPC) launched an inquiry into the pollsters' accuracy after almost every election survey during the campaign underestimated the Tories' lead over Labour.
The move comes after political observers were shocked to see last night's exit poll showing the Tories comfortably ahead of Labour as the largest party, which was then followed by David Cameron's party winning an overall majority.
GENERAL ELECTION 2015
In the run up to polling day, almost every major national poll had predicted the race was neck and neck and too close to call.
The BPC, which counts all major UK pollsters among its members, 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."
The pollsters have been criticised after offering almost universal predictions of a neck and neck race, a near-balanced parliament and a potential constitutional crisis following the General Election.
In the end, the Conservatives won an absolute majority, with 331 seats and Labour on 232, a vote share of around 37% for Mr Cameron's party and 30% for the Opposition.
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 other surveys.
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."
Meanwhile, 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."
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Andrew Cooper, of Populus, 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."Suggest a correction