By Brian Wheeler, BBC Political Reporter
Labour is set to win a general election landslide with a majority of 170, according to an exit poll for the BBC, ITV and Sky.
If the forecast is accurate, Sir Keir Starmer will become prime minister with 410 Labour MPs - just short of Tony Blair's 1997 total.
The Conservatives are predicted to slump to 131 MPs, their lowest number ever.
The Liberal Democrats are projected to come third with 61 MPs.
The Scottish National Party will see its number of MPs fall to 10, while Reform UK is forecast to get 13 MPs, according to the exit poll.
The Green Party of England and Wales is predicted to double its number of MPs to two and Plaid Cymru is set to get four MPs. Others are forecast to get 19 seats.
The exit poll, overseen by Sir John Curtice and a team of statisticians, is based on data from voters at about 130 polling stations in England, Scotland and Wales. The poll does not cover Northern Ireland.
At the past five general elections, the exit poll has been accurate to within a range of 1.5 and 7.5 seats.
If the exit poll is correct, it will be a remarkable turnaround for the Labour Party, which had its worst post-war election result in 2019, when the Conservatives under Boris Johnson won an 80-seat majority.
The Conservatives may avoid the wipe-out predicted by some opinion polls but they are still set for the worst result in the party's history, losing 241 MPs - a devastating blow after 14 years in government.
It will mean a Labour prime minister in Downing Street for the first time since 2010 and a battle for the future direction of the Conservatives if, as seems likely, Rishi Sunak stands down as leader.
The Tories are also facing an assault from the resurgent Liberal Democrats and Nigel Farage's Reform UK, which looks set to win more seats than many polls predicted.
Former attorney general Sir Robert Buckland, the first Tory MP to lose his seat as results began rolling in, told the BBC his party was facing "electoral Armageddon" and Labour's likely victory was a "big vote for change".
And he angrily lashed out at colleagues, such as former home secretary Suella Braverman, for what he called "spectacularly unprofessional and ill-disciplined" behaviour during the campaign.
"I'm fed up of personal agendas and jockeying for position," he added, warning that the upcoming Tory leadership contest was "going to be like a group of bald men arguing over a comb".
Labour's predicted landslide would be just short of the 179 majority won by Tony Blair in 1997 and the party may achieve it on a smaller share of the vote than former leader Jeremy Corbyn won in 2017, according to Sir John Curtice.
Labour shadow education secretary Bridget Phillipson, who retained her Houghton and Sunderland South seat, said: "Tonight the British people have spoken, and if the exit poll this evening is again a guide to results across our country as it so often is, then after 14 years the British people have chosen change.
"They have chosen Labour and they have chosen the leadership of Keir Starmer. Today our country with its proud history has chosen a brighter future."
In a pattern repeated in two other early results from North-East England, the Reform UK candidate came second ahead of the Conservatives by a large margin.
In a social media message, Reform UK leader Nigel Farage predicted his party was going to win "many, many seats," adding: "This, folks, is huge."
The Liberal Democrats are, meanwhile, set to squeeze the Tory vote in the south of England, where a number of Conservative cabinet members, including Chancellor Jeremy Hunt and Defence Secretary Grant Shapps, are looking vulnerable.
Liberal Democrat leader Sir Ed Davey said: "It looks like this will be our best result for a generation."
The Liberal Democrats have taken Harrogate and Knaresborough from the Conservatives, with a bigger majority than predicted by the exit poll.
Former cabinet minister Sir Jacob Rees-Mogg, who is also under threat from the Liberal Democrats, said it was "clearly a terrible night" for the Conservatives.
He said voters had been put off by the revolving door in No 10 which saw Boris Johnson replaced first by Liz Truss and then by Sunak.
Scotland's Deputy First Minister Kate Forbes said the SNP were facing a "very difficult night", as the exit poll predicted they would lose 38 seats.
"Of course we take on board what the people of Scotland, the voters, are saying in this election and we will set out our agenda to regain and rebuild the trust of voters across Scotland."
Sunak had insisted he could still win right to the end, despite failing to make a dent in Labour's commanding opinion poll lead over the six-week campaign.
Sunak surprised many in his own party by announcing a summer election.
But his campaign was hit by a series of gaffes, from the rain-drenched announcement in Downing Street to his decision to leave a D-Day celebration in Normandy early to record a TV interview and confused messaging about a Labour "super majority".
- BBC