Labour's plans to raise the minimum wage to £10 ($12.8) per hour, increase income tax for high earners and extend free meals to all primary school pupils are popular.

A ComRes poll, of more than 2,000 voters between 11 and 13 April, even found that almost three quarters of respondents (71%) supported the first pledge. But despite the UK public's support for Labour's general election promises, the party is lagging behind the Conservatives by up to 25 points in the polls.

Number Cruncher Politics founder Matt Singh, the former Barclays trader who correctly predicted that the Tories would win a majority at the last election, explained what was going on to IBTimes UK.

"Parties can often have quite popular policies, they can have a popular message. But in terms of the messenger, it can be difficult whether it is the party itself or in the particular case of Labour at the moment. Jeremy Corbyn does poll very badly across a range of groups and subsets within the electorate," he said.

"So you can have a situation where individual policies are popular, but that doesn't necessarily mean that people are going to support a party. I think a lot of it comes down to, they can agree with something or agree with an objective, but if the party doesn't have the credibility to actually go and deliver that, that can stop it translating through into support."

Singh, who is planning to release his election prediction after the local and metro mayoral elections on 4 May, said two data points have historically been the strongest predictors of how people vote: their perceptions of party leaders and their views on which party will be best on the economy.

A YouGov poll, of more than 1,600 people between 20 and 21 April, found that just 13% of respondents thought Corbyn was doing a good job as Labour leader, whilst 55% of voters said May was doing well as prime minister.

Likewise, just 19% of people said they trust Corbyn and his shadow chancellor John McDonnell on the economy. May and her Chancellor Philip Hammond, in contrast, scored 48%.

"At the moment both of those are saying pretty much the same thing," Singh said. "They very much favour the Conservatives. But, yes, Brexit has for some time now been the top issue of the list which people cite in polls on that question of which they think the most important issue is. So we'll have to see how the campaign goes."

You can watch the first part of Singh's video interview with IBTimes UK here.