General election: One in four voters could still change their minds, eve-of-poll survey shows

Almost one in four voters remain undecided over which way to cast their ballot as the country heads to the polls for one of the most important elections in a generation.

The final Ipsos Mori poll puts Boris Johnson on course for an historic win, with 44 per cent of voters backing the Conservatives, 33 per cent for Labour and 12 per cent for the Liberal Democrats. Nigel Farage's Brexit Party has been squeezed to just 2 per cent, with the Greens on 3 per cent.

If the prediction is accurate, the Tories would win the largest share of the vote at an election since Margaret Thatcher's first victory in 1979.

But nearly a quarter of voters (23 per cent) said they could still change their mind before marking their cross on the ballot paper, an increase from 19 per cent in in 2017, the survey for the Evening Standard found.

This rises to 41 per cent of Liberal Democrat supporters, while Labour supporters are more likely to wobble than Conservatives - by 25 per cent to 17 per cent.

While the Tories maintain a 11-point lead, the volatility of the electorate and potential margins of error in polls leave Mr Johnson facing the prospect of an indecisive outcome in the early hours of Friday morning.

Gideon Skinner, head of political research at the company, said there was "potential for more switching" as voters head to the polls.

"Labour has squeezed the Liberal Democrat vote share over the course of the campaign, but our final poll suggests this has not been enough to prevent the Conservatives scenting victory," he said.

"Overall, the Conservatives have managed to keep their vote from 2017 more successfully than Labour, while Boris Johnson retains his lead over Jeremy Corbyn as the most preferred PM.

"The country is not unanimous though, with clear splits by age as well as by other groups, and the number of people who said they might still change their mind is slightly higher than in 2017, with potential for more switching between Labour and the Liberal Democrats.

"And despite a record number saying the election outcome is very important to them, there are signs that the public is not wholly enthusiastic about the choices they face from either party."

Despite potential wavering from voters, 65 per cent of the 2,200 people surveyed ahead of polling day said the election result was very important to them, the highest number since Ipsos Mori first asked the question in 1987.

The research suggests the Tories will retain 85 per cent of their voters from 2017 and Labour will keep 79 per cent of its support from 2017

Mr Corbyn's party also repeats its 26-point lead over the Conservatives among young people, whilst the Conservatives hold a 37-point lead over Labour with people over 65-year-old. The Conservatives lead by 15 points with men and 6 points with women.

The polls have narrowed in the final days, as Mr Johnson's largely stage-managed election campaign was hit by a series of gaffes, including his failure to show empathy for a 4-year-old boy sleeping on a hospital floor while waiting for treatment.

Labour also suffered a setback when a recording emerged of shadow health secretary Jon Ashworth criticising Jeremy Corbyn's leadership.

Ipsos MORI interviewed a representative sample of 2,213 adults aged 18+ across Great Britain. Interviews were conducted by telephone on 9 to 11 December 2019. Data are weighted to the profile of the population.