UK front pages 2015 elections
UK front pages on the day after the 2015 elections Getty Images

It's not just the vanquished parties who will be licking their wounds this morning but the pollsters who all failed to predict an outright Conservative victory.

The Tories are poised to gain 329 seats -- more than the 326 needed to form a parliamentary majority -- a result pre-election polls called as nearly impossible, with most predicting the Tories would gain few more than 290 seats.

It is not the first time this year that the pollsters methods have come under scrutiny.

In the run-up to the Israeli elections in March, polls predicted a loss for incumbent Binyamin Netanyahu and his Likud party. In the end, Netanyahu was re-elected. Polls also predicted a narrow victory for the 'No' campaign in last year's Scottish referendum. In the event, the 'No' campaign triumphed by 11 points.

In other elections, however, pollsters' predictions have been a good guide to the eventual outcome, with surveys ahead of the 2010 election largely accurate, and polls accurately predicting the SNP's landslide north of the border this time around.

A range of reasons have been suggested for why polls can be so wide of the mark, below IBTimes surveys the chief explanations.