Nigel Farage dramatically declared he will stand to be a Reform MP and hammer the Tories tonight as a shock poll showed Labour is on track for a 194 majority.
The Brexit champion announced the U-turn and that he was taking over the leadership of the insurgents at a press conference in Westminster.
Dropping the bombshell that he will run for Parliament in Clacton, Mr Farage said the country was sick of 'sectarian politics' driven by mass immigration.
Watched by an audience including singer Holly Valance and her property developer husband Nick Candy, Mr Farage said he was back 'for the next five years' - making clear he wants to supplant the Tories as the Opposition and potentially be in power by 2029.
Mr Farage said 'not on your nelly' would he do an electoral deal with the Conservatives, predicting that Reform would win more votes on July 4.
It is a huge headache for Mr Sunak as he desperately struggled to claw back ground on Labour. Even before the shattering news from Mr Farage a YouGov poll - conducted using a technique known as MRP - was showing that Labour is on track for a bigger majority than Tony Blair, with the Conservatives reduced to just 140 seats.
A separate MRP survey by More in Common had the Labour majority at over 100, with the think-tank warning the situation is 'existential' for the Tories now Mr Farage had fully returned. The biggest fear of Tory strategists is that Reform will split the right-wing vote and hand Sir Keir and even larger victory.
A Redfield & Wilton Strategies poll this evening put the Tories on 20 per cent backing, only six points ahead of Reform and a massive 26 points behind Keir Starmer's party.
Mr Farage acknowledged that it would be 'very difficult' to win from scratch in a constituency.
But he said since the snap election was called he had been talking to people on the streets and observed that 'there is a rejection of the political class going on in this country in a way that has not been seen in modern times'.
'I rationally thought this was too difficult. I've changed my mind because I can't let down millions of people,' he said.
'Nothing in this country works... we will only recover our position with boldness,' he said. 'I've done it before, I'll do it again: I will surprise everybody.'
On the Tories he said: They are on the verge of total collapse and frankly it couldn't happen to nicer people.'
On another tumultuous day of election campaigning:
- A massive poll has projected that Labour is on track for a majority of more than 100, with think-tank More in Commons warning that Mr Farage's return poses an 'existential threat';
- Rishi Sunak vowed to change the law to allow bans on trans women using women-only spaces;
- Keir Starmer has insisted he would push the nuclear button in the last resort as he again tried to show Labour has cut ties with the Corbyn era.
Nigel Farage teased an 'emergency general election announcement' today as the campaign intensifies
Singer Holly Valance was among those in the audience at the Reform UK press conference today
Ms Valance and her property developer husband Nick Candy came to see the announcement
A Redfield & Wilton Strategies poll this evening put the Tories on 20 per cent backing, only six points ahead of Reform and a massive 26 points behind Keir Starmer's party
The Brexit champion posted on social media saying he would be dropping some news at 4pm
Explaining his change of heart, Mr Farage said: 'The other thing that really shook me in a way last week were the number of people coming up to me in the street saying 'Nigel, why aren't you standing?''
Mr Farage quickly found his previous views on Essex came back to haunt him, after he told the Times earlier this year: 'Do I want to spend every Friday for the next five years in Clacton?'
But the former MEP shrugged the comments off when they were point out to him this evening. 'You're absolutely right, it is a huge commitment,' he said.
Nigel Farage's punchiest quotes
On changing his mind:
'I simply couldn't help feeling that somehow they felt I was letting them down.
'I've changed my mind. It's allowed you know, it's not always a sign of weakness. It could potentially be a sign of strength.
'So I am going to stand in this election. I'll be launching my candidacy at midday tomorrow in the Essex seaside town of Clacton...
'Richard (Tice) is more than happy for me to put my head and shoulders firmly over the parapet and take the flack so I'm coming back as leader of Reform UK, but not just for this election campaign. I'm coming back for the next five years.'
On immigration:
'We're worried and we're fearful of many of the impacts that we've seen. We find what happened after those local elections just a few weeks ago, of candidates winning in Leeds, in Burnley, in Bradford and elsewhere, standing shouting 'Allahu Akbar', standing shouting 'we are coming to get you'.
'The birth of sectarian politics in our country caused by massively irresponsible immigration policies. And it was the Labour Party that opened the door and who would have believed that a Conservative Party would have accelerated it.'
On the Tories:
'They are split down the middle on policy, and frankly, right now they don't stand for a damn thing.
'So our aim in this election is to get many, many millions of votes. And I'm talking far more votes than Ukip can got back in 2015.'
He continued: 'When people start to realise in the red wall, with Reform second to Labour, when they start to realise that actually in those seats, it's a Conservative vote that's a vote for Labour, it's a Conservative vote that is a wasted vote, then I think we might just surprise everybody.'
On the election campaign so far:
'We put out the operations notice for today under the title 'emergency election announcement'.
'We did that because we think this election needs a bit of gingering up. Thus far, it is the dullest, most boring election campaign we have ever seen in our lives.
'And it's funny because the more the two big party leaders try to be different, the more they actually sound the same.'
Frenzied speculation about Mr Farage's intentions was sparked this morning when he posted on social media about an 'emergency general election announcement'.
There were immediately rumours that Clacton or East Thanet had attracted his eye.
Reform has already selected a candidate in Clacton, but they will stand aside.
Mr Farage suggested that 'massively irresponsible immigration policies' have caused 'the birth of sectarian politics in our country'.
The new Reform UK leader said: 'We're worried and we're fearful of many of the impacts that we've seen. We find what happened after those local elections just a few weeks ago, of candidates winning in Leeds, in Burnley, in Bradford and elsewhere, standing shouting 'Allahu Akbar', standing shouting 'we are coming to get you'.
'The birth of sectarian politics in our country caused by massively irresponsible immigration policies. And it was the Labour Party that opened the door and who would have believed that a Conservative Party would have accelerated it.'
Mr Farage said he ''genuinely believes we can get more votes in this election than the Conservative Party'.
'They are on the verge of total collapse,' he said.
Asked whether he has boosted Sir Keir Starmer's chances by running for parliament, the new Reform leader said: 'No, is the answer.'
He added that in a week's time, 'I think you'll see we're going to start drawing from Labour equally as much as the Conservatives.
'The Conservative Party have lost this election without my intervention.'
Mr Farage said 'this political party to become the voice of opposition in the next parliament' which he claimed the Conservatives are 'incapable' of being.
He said he wanted to lead a 'political revolt'.
'Yes, a revolt. A turning of our backs on the political status quo. It doesn't work. Nothing in this country works any more,' he said.
On the Tories he said: 'They are split down the middle on policy, and frankly, right now they don't stand for a damn thing.
'So our aim in this election is to get many, many millions of votes. And I'm talking far more votes than Ukip can got back in 2015.'
He continued: 'When people start to realise in the red wall, with Reform second to Labour, when they start to realise that actually in those seats, it's a Conservative vote that's a vote for Labour, it's a Conservative vote that is a wasted vote, then I think we might just surprise everybody.'
He added: 'We are appealing to Conservative voters, we are appealing to Labour voters.'
A Tory spokesman said: 'Nigel Farage risks handing Keir Starmer a blank cheque to rejoin the EU, impose the Retirement Tax on pensioners and hike taxes on hardworking Brits up and down the UK.
'Farage knows that Reform won't win any seats, but he doesn't seem to care that a vote for Reform only helps Labour. He's doing exactly what Keir Starmer wants him to do.
'Just yesterday, EU insiders openly voiced their expectation that Starmer would seek a softer Brexit deal, opening the door to rejoining the EU all together. That would mean uncontrolled immigration and betraying the will of the British people.'
Is Farage really willing to risk undoing his life's work by handing Starmer a blank cheque to rejoin the EU?
The new YouGov poll for Sky News found Labour is in course for the biggest election victory in history, beating Tony Blair's 1997 landslide.
The potential Tory tally of 140 would be far fewer than the previous lowest number of Conservative seats in recent history - 165 in 1997.
A Labour majority of 194 would be the highest since Stanley Baldwin's 208 in 1924.
The MRP - multi-level regression and post-stratification - technique maps demographic characteristics of voters on to seats, to give the best possible picture of how local contests will go.
It suggested that Sir Keir Starmer's party is on course to win 422 seats, with the Tories down to just 140.
Luke Tryl, executive director of More In Common, said Mr Farage would 'have a very good chance in Clacton'.
'It's one of those seats that has really moved away from the Labour Party in recent years,' he told LBC's The News Agents podcast.
He added: 'If you look at that combination of cynicism, that particular seat, Nigel Farage's profile, I think he could have a very good chance in somewhere like Clacton.'
The intervention came after Kemi Badenoch ruled out serving in the Tories if Mr Farage joined after the election.
The Cabinet minister hit out after Mr Farage alarmed moderates by suggesting he will 'take over' the Conservatives after a heavy election defeat on July 4.
Mr Farage kept Westminster guessing for months before announcing shortly after the election was called that he would not be a candidate.
He blamed Mr Sunak's decision to go early for his stepping aside, admitting he did not have time to build a campaign in a seat.
Clacton was previously held by Douglas Carswell for UKIP.
In January a Survation poll in the constituency suggested that Mr Farage could defeat Tory incumbent Giles Watling.
There are widespread fears among Conservative MPs that Reform will hand Labour a bigger victory by splitting the right-wing vote on July 4.
Mr Farage joined Reform leader Richard Tice on the campaign trail in Skegness, Lincolnshire over the weekend.
Asked whether he wanted to facilitate a merger with the Tories after the election, he replied that it was 'more like a takeover, dear boy'.
Mr Farage has suggested he wants to engineer a realignment of the Right so Reform can team up with Tory hardliners.
In a round of interviews, this morning Ms Badenoch was asked if she would carry on with Mr Farage as a colleague.
'No, no, Nigel Farage has stood against many Conservatives, including some of my colleagues, what he wants to do is destroy the Conservative Party,' she told LBC.
Ms Badenoch insisted the Tories were an 'institution' and needed to keep going from 'strength to strength'.
Recently-ousted West Midlands mayor Andy Street warned yesterday that the Conservatives can only win from the 'middle ground', saying the idea that Mr Farage should be a leading figure was 'nonsense'.
Mr Street told the BBC's Laura Kuenssberg on Sunday programme that the fact he came close to keeping his job in traditional Labour territory despite grim national polls demonstrated that the Tories needed to keep to the 'centre ground'.
'Whether we win or lose the general election the point is simple, that you have to have that broad church. You have to be centred in the middle ground,' he said.
'The lesson of history… the winners have come from the centre ground.'
Mr Street - who decided against standing to become an MP - said that the top echelons of government was dominated by centrists, but added: 'Who knows what the composition might be and the temptation might be in the future.'
He dismissed 'nonsense' rumours that Mr Farage will be among the leaders after the election.
'That is not a moderate inclusive Conservative Party with a broad appeal. That's why it's appropriate that we think about this well before we know the oucome of any general election,' he said.
The clashes came as a poll showed Labour extending its lead to 20 points - the biggest advantage since Liz Truss was PM.
The Opinium research found Sir Keir's party was on 45 per cent while the Tories had dropped to 25 per cent. A week earlier, before the first stages of campaigning, the firm detected a 14-point gap.
Earlier this week, Mr Farage declared he had 'no interest' in striking a pre-election deal with the Tories.
He dismissed comments he previously made where he said they 'might have a conversation' as 'deeply sarcastic'.
'There is no deal with the Conservatives whatsoever,' Mr Farage told a press conference.
The Prime Minister has also ruled out a deal with Reform, despite the insurgent party putting huge pressure on the Tories over issues such as the Channel migrant crisis.
Reform said the press conference would be attended by leader Richard Tice as well
Kemi Badenoch hit out after Mr Farage alarmed moderates with the suggestion he will exploit a heavy election defeat on July 4
Rishi Sunak has ruled out a deal with Reform, despite the insurgent party putting huge pressure on the Tories over issues such as the Channel migrant crisis
Recently-ousted West Midlands mayor Andy Street warned yesterday that the Conservatives can only win from the 'middle ground'
Reform UK is currently polling between 12 and 15 per cent but Farage has said that Tice's party must reach 18 per cent if they are going to win seats in Parliament.
The right-wing party is offering tax cuts, the abolition of business rates for small businesses, and tax relief for private healthcare users in the draft of its July 2024 election manifesto.
Reform UK are also pledging to launch more public inquiries into Covid-19 and the rollout of the vaccine.