Nearly half of those who voted for Labour in 2015’s general election say they will support a different party on 8 June, according to pollsters YouGov, while three-quarters of Conservative voters will be sticking with the Tories.

Previous Ukip and Liberal Democrat voters are switching allegiance in even greater numbers, a new poll suggests, as one in five voters across all parties plans to take their support elsewhere.

The unusually high rate of “churn” between political parties is being linked to last year’s EU referendum, and is set to hit Jeremy Corbyn’s Labour party considerably harder than Theresa May’s Conservatives.

(YouGov (YouGov)

The figures come as a new poll shows that the Conservative lead over Labour has shrunk by seven points, with the Tories currently set to secure 45 per cent to their rival’s 29 per cent.

12,000 people responded to the survey, of whom 57 per cent say they plan to vote the same way as they did in 2015, when David Cameron won an unexpected outright victory over Ed Miliband.

But 22 per cent of the public intend to take their vote elsewhere, while 20 per cent are still undecided.

The Tories are set to retain 77 per cent of their voters, compared to just 52 per cent for Labour. The Liberal Democrats and Ukip will only hang on to 47 per cent and 43 per cent respectively.

Explaining the results, YouGov political researcher Chris Curtis said: “Such a high level of voter churn is unusual, especially given it is not very long since the last general election.

“However, the EU Referendum seems to have caused a significant realignment within a brief space of time with many voters finding their own views on Brexit are out of step with the views of the party they voted for in 2015.”

(YouGov (YouGov)

Breaking down the results by vote in last year’s EU referendum, it can be seen that many Leave voters are joining the Tories from Ukip and to a lesser extent Labour, while many defeated Remain voters are drifting toward the Lib Dems from Labour.

A small but significant number of Remainers also switched to Tim Farron’s party from the Greens.

Ms May, who replaced Mr Cameron as Prime Minister shortly after last June’s EU referendum shock, repeatedly ruled out a snap election until she announced the 8 June vote last week.

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She is seeking to bolster her majority in Parliament ahead of potentially disruptive EU divorce talks.

Mr Curtis said: “How and if these voters break over the coming weeks will determine the final result, especially in marginal constituencies. Were they to drift back to the party they voted for last time, this would disproportionately help Labour (as that is where many of them have come from).