Hung parliament threat looms as final day of campaigning begins

Boris Johnson will go into the final full day of campaigning looking to win "every vote" after a fresh poll suggested a hung parliament could still be on the cards.

YouGov's constituency-by-constituency poll predicts the Conservatives are on course for a 28 seat majority – but the margin of error and unknown impact of tactical voting means a hung parliament is still a possibility.

The pollsters, who have analysed more than 100,000 voter interviews over the past week, predicted the Tories will win 339 seats and Labour 231.

A 28-seat majority would be the best Tory result since Margaret Thatcher's showing in 1987 – but it is down from the sizeable 68-seat victory that the same YouGov-style poll had been predicting only two weeks ago.

Chris Curtis, YouGov's political research manager, said: "The margins are extremely tight and small swings in a small number of seats, perhaps from tactical voting and a continuation of Labour's recent upward trend, means we can't currently rule out a hung parliament."

The result will be a worry to Mr Johnson as he prepares for a final blitz across the country as the campaign enters its final full day, with Tory gains off Labour reduced from 44 to 29 since the November 27 findings.

The Tory leader told journalists at an event at JCB's Cab Manufacturing Centre in Staffordshire he was "absolutely not" guaranteed victory on Thursday

"This is a very close fought election and we need every vote," he said.

Mr Johnson will spend the final day of campaigning in Labour marginals in Yorkshire, the Midlands and Wales, before finishing the day with a rally near London.

While the polls have improved for Jeremy Corbyn's Labour Party, the haul of 231 seats would mean a loss of 31 seats compared to 2017's outcome – its worst result since the 1980s.

According to YouGov, Labour could be set to make two gains, pulling off a Cabinet minister scalp by taking Chipping Barnet, the constituency currently held by Environment Secretary Theresa Villiers.

Foreign Secretary Dominic Raab is in trouble to the Liberal Democrats in Esher and Walton, while former Tory leader Iain Duncan Smith in Chingford and Woodford Green is clinging on by only two points against Labour, the poll result indicates.

Putney could also go red but YouGov continues to predict a tough time for Labour in its heartlands in the North and Midlands.

Veteran MP Dennis Skinner's Bolsover seat could be taken by the Tories, as could constituencies such as Great Grimsby, a Leave-voting town represented by Labour since the Second World War.

The SNP would win 41 seats – up by six – and the Liberal Democrats 15 if the prediction bears out.

Plaid Cymru would hold onto its four constituencies and the Green Party its one, while Nigel Farage's Brexit Party would finish the election empty handed, polling predicts.

YouGov uses multilevel regression and post-stratification (MRP) to form its predictions – a model that predicted 93% of constituencies correctly in the snap election two years' ago.

The polling company first models voting preferences based on age, gender, education and previous votes, along with local political circumstances, before applying MRP, a technique which adds local factors and individual characteristics of each of Great Britain's 632 constituencies to come up with its final result.