Sir Keir Starmer is set to be swept to power by a landslide Labour victory as bitter recriminations began in the Tory ranks.
Labour is forecast to have a 170-seat majority in the Commons, with the Conservatives reduced to their lowest number of MPs on record.
If the results indicated by an exit poll are accurate, Rishi Sunak’s term as Prime Minister will end in electoral disaster, with Nigel Farage’s Reform UK establishing a foothold in Parliament and the Liberal Democrats forecast to make significant gains.
Shadow education secretary Bridget Phillipson held Houghton and Sunderland South in the first result of the night, but Reform pushed the Conservatives in an early indication of the advances made by Mr Farage’s party.
Ms Phillipson, who will now expect to be in Sir Keir’s first Cabinet, 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.”
The exit poll suggests Labour is on course for 410 seats, with the Tories reduced to 131.
The Liberal Democrats are forecast to win 61 seats, Reform UK on 13 and the Green Party two.
In Scotland, the SNP are expected to secure 10 seats with Plaid Cymru in Wales on four.
The poll for broadcasters involved more than 20,000 voters at 133 polling stations.
If the results follow the forecast, it will mean a Labour prime minister in No 10 for the first time since 2010 and the Conservatives facing a fight for the future direction of the party.
Former justice secretary Sir Robert Buckland was the first high-profile casualty as he lost to Labour in Swindon South.
He warned that a lurch to the right after the election would be “disastrous” for the Conservatives and took aim at “ill-discipline” within the Conservative Party after losing his seat.
“I think that we have seen in this election an astonishing ill-discipline within the party,” the former justice secretary told the BBC.
“We can see articles being written before a vote is cast at the General Election about the party heading for defeat and what the prognosis should be.
“It is spectacularly unprofessional, ill-disciplined. That is not the Conservative Party I joined and have been an active member of for now nearly 40 years.”
Asked later if he was speaking about an article written by Conservative former home secretary and potential leadership contender Suella Braverman, Sir Robert replied: “I am afraid that is not an isolated example.”
Former Cabinet minister Sir Jacob Rees-Mogg said it is “clearly a terrible night”, suggesting voters had been put off by the revolving door in No 10 which saw Boris Johnson replaced first by Liz Truss and then by Mr Sunak.
Sir Jacob told the BBC “there were issues with changing the leader”, adding: “Voters expect the prime minister they have chosen to remain the prime minister and for it to be the voters who decide when that person is changed.”
After 14 years in power, it was always going to be a difficult election for the Conservatives, but the sometimes shambolic campaign – triggered at a time of Mr Sunak’s choosing – has contributed to the party’s likely defeat.
From the rain-drenched speech announcing the surprise July 4 poll, through the D-Day debacle as he left Normandy early to record a TV interview to confused campaign messaging about a Labour “supermajority”, Mr Sunak struggled to convince the electorate he was the right man to lead the country.
Going for a summer election rather than waiting until the autumn was always a gamble, and the Prime Minister was not helped by the scandal of Tory candidates and officials allegedly heading to the bookies armed with inside knowledge of the date.
Mr Sunak is expected to resign after leading his party to defeat, but many of the contenders jostling to replace him are nervously awaiting their own constituency results to see if their leadership dreams survive the night.
The likes of Penny Mordaunt, Grant Shapps and Steve Baker all face battles to return to Parliament, while Chancellor Jeremy Hunt is predicted to lose.
A Liberal Democrat source said they were “confident” of defeating the Chancellor in the Godalming and Ash seat in Surrey.
And the party claimed it had defeated Education Secretary Gillian Keegan in Chichester and Justice Secretary Alex Chalk in Cheltenham.
Meanwhile, Nigel Farage said Reform would win “many, many seats” across the country.
He added: “This is going to be six million votes plus. This, folks, is huge.”
Lee Anderson, who defected from the Tories, became the party’s first elected MP as he won in Ashfield – with the Conservatives in fourth place behind Labour and an independent.
Lib Dem leader Sir Ed Davey said his party was “on course for our best results in a century”.
In Rochdale, Workers’ Party leader George Galloway lost the seat he won in a by-election earlier this year.
The SNP’s campaign centred around calls for talks on another independence referendum if the party won a majority of seats at the election.
Despite the exit poll result, Deputy First Minister Kate Forbes told the BBC: “I would strongly caution anybody against dismissing the robust, resilient and significant number of people in this country that support independence and the next Labour government will have to contend with that, we’ll have to listen to Scottish voters because even over the last few months – which have been difficult – that support for independence has remained strong.”
But she added the party would need to “listen to the voices of voters” and “set out our agenda to regain and rebuild the trust of the voters across Scotland”.
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