She was replying to Ms Whittome’s post which said: ‘No matter your views on her stated reasons for quitting, Rosie Duffield has made a political career out of dehumanising one of the most marginalised groups in society.

‘She should never have been allowed the privilege of resigning. Labour should have withdrawn the whip long ago.’

Ms Duffield reposted Rowling’s post defending her, and replied to Ms Whittome saying: ‘Stay classy Nadia x’

In Ms Duffield’s explosive resignation letter to Sir Keir Starmer, she criticised his ‘cruel and unnecessary policies’ including the decision to keep the two-child benefit cap and means-test the winter fuel payment, while accusing the Prime Minister of ‘hypocrisy’ over his acceptance of free gifts from donors.

Ms Duffield blasted the PM for throwing the electorate’s ‘sacred and precious trust’ in its face ‘and in the faces of Labour MPs’.

She also used her letter to deliver a scathing attack on Sir Keir’s leadership style, including his ‘various heavy-handed management tactics’, adding he had shown neither ‘true nor inspiring leadership’.

In the letter published by the Sunday Times she said: ‘Since the change of government in July, the revelations of hypocrisy have been staggering and increasingly outrageous.

‘I cannot put into words how angry I and my colleagues are at your total lack of understanding about how you have made us all appear.’

She added: ‘The sleaze, nepotism and apparent avarice are off the scale. I am so ashamed of what you and your inner circle have done to tarnish and humiliate our once proud party.’

The Tories have since rounded her decision to leave the Labour Party, with Tom Tugendhat saying it demonstrates the Government is ‘about self-service’.

As he arrived at Conservative Party Conference, the Tory leadership hopeful told the BBC: ‘I think she has made her point very clearly hasn’t she?

‘Which is that the Labour Party and Keir Starmer’s Government is not about service, it is not about delivering for the British people, it is about self-service.

‘We need to return our government to service, we need to demonstrate the leadership that this country needs, and that is exactly what I am here to do.’

Asked if he would invite Ms Duffield to join the Conservatives, Mr Tugendhat said: ‘That is really a decision for her, but I think she is an extraordinary voice, she has stood up for women’s rights, she stood up for the dignity of individuals across our country, and I think she is a fantastic advocate.’

Pressed again on the matter, he said Ms Duffield has been a ‘socialist for many years’, adding: ‘I strongly suspect she won’t be asking.’

Ms Duffield was first elected as a Labour MP in the 2017 snap election, taking the Kent seat from the Conservatives.

She started her letter: ‘Usually letters like this begin ‘It is with a heavy heart… ‘. Mine has been increasingly heavy and has longed for a degree of relief.

‘I can no longer stay a Labour MP under your management of the party.’

She added that while there had been many ‘last straws’, but accused the PM of stressing ‘tough decisions’ that ‘do not directly affect any one of us in Parliament’.

She continued: ‘This is not what I was elected to do. It’s not even wise politics, and it certainly is not ‘the politics of service’.

The MP further hinted in her letter that she didn’t support Sir Keir to become Labour leader in 2020, because of the PM’s little ‘previous political footprint’, suggesting he had gained a shadow cabinet position without ‘the usual path of honing your political skills on the backbenches’.

She also attacked the PM’s ’embarrassing’ promotion of people without ‘proven political skills and no previous parliamentary experience, but who happen to be related to those close to you’.

She wrote: ‘As Prime Minister, your managerial and technocratic approach, and lack of basic politics and political instincts, have come crashing down on us as a party after we worked so hard, promised so much, and waited a long fourteen years to be mandated by the British public to be returned to power.

How dare you take our longed-for victory, the electorate’s sacred and precious trust, and throw it back in their individual faces and the faces of dedicated and hardworking Labour MPs?!

‘The sleaze, nepotism and apparent avarice are off the scale. I am so ashamed of what you and your inner circle have done to tarnish and humiliate our once proud party.’

Her letter continues: ‘I now have no confidence in your commitment to deliver on the ‘so-called’ change you promised during the General Election campaign and the changes we have been striving for as a political party over a decade.’

Ms Duffield also attacked Sir Keir’s record on antisemitism, claiming he left speaking up against former leader Jeremy Corbyn to ‘backbenchers like me’, while taking aim at the Prime Minister’s ‘heavy-handed management tactics’.

And in an attack on the wider party, she accused Labour of showing no interest ‘in my wonderful constituency’ during her seven years in the Commons.

She finished by saying that she hoped to return to Labour when it ‘resembles the party that I love’.

‘As someone who joined a trade union in my first job, at seventeen, Labour has always been my natural home.

‘Right now, I cannot look my constituents in the eye and tell them anything has changed. I hope to be able to return to the party in the future, when it again resembles the party I love, putting the needs of the many over the greed of the few.’

In July, the MP spoke out against Sir Keir’s support of the ‘overtly sexist’ two-child benefit cap, which she likened to something from Margaret Attwood’s novel The Handmaid’s Tale.

She has also previously criticised the Prime Minister’s position on gender ideology.

Her resignation comes after a difficult week for the Government, as a row over ministers accepting freebies from donors deepened on Friday with the revelation that Sir Keir had received another £16,000 in free clothes from Labour peer Lord Alli.

It brought the total amount accepted by the Prime Minister for clothing from Lord Alli to £32,000.

Questions have also mounted over Sir Keir’s use of the Labour peer’s £18million penthouse flat in Covent Garden, where the PM stayed during the election period in June, and also recorded clips advising Britons to stay at home during the pandemic, and a tribute to the late Queen Elizabeth II following her death in 2022.

Labour has also refused to answer queries over Lord Alli’s Downing Street pass, since withdrawn, which previously allowed him to attend meetings on national security grounds.

The Prime Minister is also facing accusations of having a conflict of interest in accepting Arsenal football tickets and hospitality – all while his government is about to introduce legislation to create a regulator for the sport.