Why is there such a wild difference in latest election polls?

Opinion polls have infamously failed to predict vote results in recent years - but some of the current ones are destined to be proved wrong on June 9.

That's because they are predicting wildly different outcomes a day after the nation votes in the 2017 General Election.

One respected opinion poll by YouGov forecasts a hung parliament while another by ComRes has the Tories returned with a 100-seat majority.

2015's General Election and 2016's EU referendum and US presidential election all delivered results that contradicted the ballot box predictions.

So are we right to dismiss the latest polls or can they still be seen as reliable? And why are they so volatile at the moment?

ITV News election analyst Professor Colin Rallings, of Plymouth University, gives his thoughts on the ever-changing predictions.

  • There's a huge discrepancy in the polls at the moment, why is that?

It's quite interesting. At the last election the polls were accused of 'herding', that is everyone telling you the same story.

This time there are many different results and indeed there has been a very big change since the start of the campaign.

Theresa May's predicted fortunes have fluctuated since she called for a snap election. Credit: PA

What seems to be happening is that many of the pollsters are interpreting who is going to turn out to vote rather differently.

So if for example you think that older people are more likely and more certain to vote then you get a different outcome than if you assume that younger people's turnout will be slightly larger than it has been historically.

  • How different are the polls now to this point at the last election?

Two years ago the Conservative majority took everyone by surprise.

That's because the polls were really very narrow between the Conservatives and Labour and many people even assumed that Ed Miliband would be the prime minister, at least as leader of the largest party.

Ed Miliband was projected to claim power two years ago. Credit: PA

That's what the polls were suggesting with a week to go last time but the result was different.

The result could be different to what the polls are saying this time as well.

  • A couple of weeks ago everyone was predicting a Tory landslide. Now there has been a surge by the Labour party. Why?

I think the Conservatives, when Mrs May called the election, hoped it would be about Brexit, hoped it would be about leadership, hoped it would be about competence.

What Labour and Jeremy Corbyn have managed to do is to get the conversation onto the subject of public services.

Jeremy Corbyn has focused his campaign on the future of schooling and the NHS. Credit: PA

Labour have always been stronger in terms of public services and their policies and what they would claim as their record defending them.

As people begin to think about what their future may look like after Brexit I think maybe they are a little worried about the stark picture many on the Conservative side would perhaps paint.

  • What sort of turnout are we likely to see and what's going to affect the result?

Turnout is going to be key in terms of the result on polling day.

It was the same in the referendum on the EU - people said if young people vote in numbers then we will vote to remain, if they don't we'll vote to leave.

The turnout across different generations could help decide the election. Credit: PA

History tells us older people are much more likely to vote than younger people and if that disparity continues at this election the better the chance for the Conservatives. They want older people to vote. Labour want younger people to vote.

You'll see that reflected in the kinds of people that the parties are trying to encourage onto their side in the last few days.

  • What's your prediction?

Shut the camera down. (laughs) I don't know.