Amber Rudd has sensationally quit the UK's Cabinet and the Conservative Party in protest at Boris Johnson's handling of Brexit.
In a tweet, Ms Rudd declared: "I cannot stand by as good, loyal moderate Conservatives are expelled.
"I have spoken to the PM and my Association Chairman to explain. I remain committed to the One Nation values that drew me into politics."
The Hastings and Rye MP quit her post as work and pensions secretary and said she was relinquishing the Tory whip after the Prime Minister sacked 21 rebels this week.
Ms Rudd has become the latest of more than 20 Tory MPs to have quit or been kicked out of their party during a week of tumultuous Brexit politics.
Phillip Lee, the pro-remain MP for Bracknell, crossed the floor of the House of Commons to join the Lib Dems on Tuesday, leaving Prime Minister Boris Johnson without a working majority in Parliament.
After rebelling over Brexit, two former chancellors were among 21 Tories to be stripped of the Conservative whip in a retaliatory move by Mr Johnson.
The Prime Minister ordered the whip removal on Tuesday after the MPs backed a plan to take control of the Commons timetable to pass legislation to block a no-deal Brexit.
I have resigned from Cabinet and surrendered the Conservative Whip.
— Amber Rudd MP (@AmberRuddHR) September 7, 2019
I cannot stand by as good, loyal moderate Conservatives are expelled.
I have spoken to the PM and my Association Chairman to explain.
I remain committed to the One Nation values that drew me into politics. pic.twitter.com/kYmZHbLMES
Upon the news of Ms Rudd's resignation, David Gauke, the former secretary of state for justice and lord chancellor, tweeted: "I'm sure this has not been an easy decision. But it is brave and
principled and is all about putting the national interest first."
Former minister Damian Green added that the news was "desperately sad".
Health Secretary Matt Hancock tweeted: "So sorry to see Amber resign - a first-rate minister, genuinely wonderful person, and someone I'm proud to call my friend.
"The Conservative party has always been a broad church shaped by those within it. Gutted to see Amber leave - but hope other One Nation Tories will stay and fight for the values we share."
Meanwhile, Brexit Party leader Nigel Farage tweeted: "Why did Boris give ministerial posts to all these Remainers in the first place? Confused thinking to say the least."
Why did Boris give ministerial posts to all these Remainers in the first place? Confused thinking to say the least. https://t.co/rhbVnAlmrK
— Nigel Farage (@Nigel_Farage) September 7, 2019
In her letter to Prime Minister Boris Johnson, Amber Rudd said she was resigning with "great sadness", but that she no longer believes getting a deal from the EU is the Government's main objective.
The full letter said: "It is with great sadness that I am resigning as Secretary of State for Work and Pensions and Minister for Women and Equalities.
"It has been an honour to serve in a department that supports millions of people and can be such a force for good. I would like to pay tribute to the thousands of people who work for the DWP across the country. They are committed public servants and I am proud of the work that we have done together over the last 10 months to create a more compassionate welfare system.
"I would also like to thank you and the Chancellor of the Exchequer for your support in the recent Spending Review. I am so pleased that you committed to spend millions more supporting the most vulnerable in society, and I hope that the Government will stay committed to going further at the next fiscal event, building on the work the department has done.
"This has been a difficult decision. I joined your Cabinet in good faith; accepting that 'no deal' had to be on the table, because it was the means by which we would have the best chance of achieving a new deal to leave on October 31.
"However, I no longer believe leaving with a deal is the Government's main objective.
"The Government is expending a lot of energy to prepare for 'no deal' but I have not seen the same level of intensity go into our talks with the European Union, who have asked us to present alternative arrangements to the Irish backstop.
"The updates I have been grateful to receive from your office have not, regretfully, provided me with the reassurances I sought.
"I must also address the assault on decency and democracy that took place last week when you sacked 21 talented, loyal One Nation Conservatives.
"This short-sighted culling of my colleagues has stripped the party of broad-minded and dedicated Conservative MPs I cannot support this act of political vandalism.
"Therefore, it is with regret that I am also surrendering the Conservative whip.
"Britain's body politic is under attack from both sides of the ideological debate. I will now play whatever role I can to help return it to a better place.
"I have been lucky to have had extraordinary support from my Conservative Association since I was adopted as their candidate in 2006. Three times they helped elect me as their MP, keeping Labour at bay through nail-biting campaigns.
"I remain a proud conservative and will continue to champion the values of fairness and compassion, and to support my constituents of Hastings and Rye.
"Yours Sincerely,
"Amber Rudd."
