Dominic Raab has dramatically quit as deputy Prime Minister after Rishi Sunak dithered over whether to sack him.
In his resignation letter, bitter Mr Raab took a furious swipe at the findings of a bombshell bullying report, describing them as "flawed" and claiming they set a "dangerous precedent".
He now faces calls to quit as an MP, forcing a by-election in his Esher and Walton constituency.
Labour has hit out at Mr Sunak's "indecision and weakness" in allowing Mr Raab to quit rather than sacking him.
Number 10 declined to say whether the deputy PM was asked to resign, or whether he would otherwise have been sacked.
It comes after a long-awaited report by top lawyer Adam Tolley was delivered to Downing Street following 15 allegations about Mr Raab's behaviour.
In a letter to the PM, Mr Raab said all but two of the claims had been dismissed, and bitterly wrote that ministers "must be able to give critical feedback" to officials.
It saves weak Mr Sunak a mammoth decision that was set to split the party, with critics branding his delay in acting a "farce".
While Mr Raab's critics and accusers demanded his sacking,his allies initially said he he intended to "fight to the death" to stay in post.
However this morning he finally accepted the game was up, fuming: "In setting the threshold for bullying so low, this inquiry has set a dangerous precedent."
He wrote: "Whilst I feel duty bound to accept the outcome of the inquiry, it dismissed all but two of the claims levelled against me.
"I also believe that its two adverse findings are flawed and set a dangerous precedent for the conduct of good government."
The probe into deputy Prime Minister and Justice Secretary Mr Raab's behaviour was opened back in November following allegations from officials who had worked under him.
The Mirror reported that staff involved in the complaints said they lost weight, suffered breakdowns or even felt suicidal as they thought there was no escape.
Mr Raab maintained he had done nothing wrong, but in February said he would step down from the Cabinet if any bullying allegations were upheld.
He spoke to Mr Sunak this morning before announcing his resignation, but the PM's official spokesman refused to disclose what was said between the two.
Downing Street suggested that Mr Sunak accepts Mr Raab broke the Ministerial Code with the finding of bullying.
The PM's spokesman said: "You can see the aspects relevant to the code are set out in the report. I think those speak for themselves.
"The Prime Minister thinks it's right that any findings whatsoever that are deemed to be bullying, it's right to resign. That's the commitment the former secretary of state made and he's upheld that commitment."
In his letter Mr Raab said Mr Tolley had accepted he had never shouted or sworn at anyone, thrown anything or physically intimidated anyone.
He wrote: "I am genuinely sorry for any unintended stress or offence that any officials felt, as a result of the pace, standards and challenge that I brought to the Ministry of Justice.
"That is, however, what the public expect of Ministers working on their behalf."
He claimed that the outcome would open the door to "spurious" complaints against ministers.
Labour leader Keir Starmer has said Mr Sunak's "indecision and weakness" in allowing his deputy to resign "goes to the heart" of the "failure" of successive Tory governments.
Speaking to broadcasters, he said: "Why didn't he sack him? And now it's left for Dominic Raab to resign because the Prime Minister hasn't acted.
"It's that indecision and it's that weakness that goes to the heart not just of this Prime Minister but 13 years now of failure."
The Liberal Democrats have demanded a by-election in his constituency, with deputy leader Daisy Cooper saying: "Dominic Raab has shown he is not only unfit to serve as a minister, but is totally unfit to represent his constituents in Parliament.
"He should resign as an MP and trigger a by-election so the people of Esher and Walton can finally have the MP they deserve."
In a 1,100 word rant published by The Daily Telegraph, Mr Raab claimed to have been warned about a plot against him by Whitehall officials.
He wrote: "This precedent sets the playbook for a small number of officials to target ministers, who negotiate robustly on behalf of the country, pursue bold reforms and persevere in holding civil servants to account.
"If that is now the threshold for bullying in government, it is the people of this country who will pay the price."
One MP voicing her support was Tory Joy Morrissey, who said she was "totally gutted" by Mr Raab's departure.
She wrote; "Sadly, we now live in a country where the definition of bullying includes telling someone to do their job. Where the slightest upset or annoyance is indulged with endless reports and inquiries.
"Where whining, taking offence and narcissistic victimhood have become the defining characteristics of our times - as the uncomplaining and silent majority look on in disbelief..."
Mr Raab is the third high-profile cabinet departure since Mr Sunak took office in October promising a Government of "integrity, professionalism and accountability at every level".
He sacked Nadhim Zahawi as Conservative Party chair amid controversy over his tax affairs, while Sir Gavin Williamson - another Sunak backer - resigned after it was alleged he sent expletive-laden messages to a former chief whip.
The Mirror has previously reported Mr Raab has been nicknamed “The Incinerator” because he “burns through” staff so quickly.
It was alleged that in one instance he had hurled tomatoes across a table in a rage, but Mr Tolley said there was no evidence to support this.
Mr Sunak, who reappointed him to the Cabinet after he was sacked by Liz Truss, resisted calls to suspend his deputy while the probe was carried out.
Mr Raab told Sophy Ridge on Sunday earlier this year: "Look, if an allegation of bullying is upheld, I will resign."
Asked whether he is a bully, he replied: "No."
An insider told The Guardian that if Mr Raab remained in post, many senior civil servants were likely to quit.
They said: “If he stays in the department, senior people will want to walk.”
But one cabinet member - who was not named - told TalkTV: 'We can't just throw our own people to the dogs because the civil service say so."
Former Tory chairman Jake Berry has repeatedly called for Mr Raab to be suspended while the investigation is carried out. He told ITV's Robert Peston: 'It does seem to me quite wrong that when people are under these kinds of investigations of this type that they continue in their job."
