Britain's Work and Pensions Secretary Iain Duncan Smith has resigned, citing concerns about the latest round of cuts to benefits announced in a budget update earlier this week.
UK media cited Duncan Smith's resignation letter, which said he had made the decision over cuts to disability payments.
"I have for some time and rather reluctantly come to believe that the latest changes to benefits to the disabled and the context in which they've been made are, a compromise too far," Duncan Smith wrote in his resignation letter.
"While they are defensible in narrow terms, given the continuing deficit, they are not defensible in the way they were placed within a budget that benefits higher earning taxpayers," the letter said.
"They should have instead been part of a wider process to engage others in finding the best way to better focus resources on those most in need."
"I am unable to watch passively whilst certain policies are enacted in order to meet the fiscal self imposed restraints that I believe are more and more perceived as distinctly political rather than in the national economic interest."
Chancellor George Osborne came under pressure from other members of his own party earlier on Friday to rethink the plan.
Duncan Smith was praised by Tory MP Peter Bone, who said: "IDS has always been a man of conviction! Tonight, yet again he put the country first."
Fellow MP Andrew Percy, who had led a Conservative backbench revolt against the cuts, wrote on Twitter: "Credit to IDS. I'll say no more tonight but all is not as it has seemed in the past few days."
Opposition Labour leader Jeremy Corbyn said the resignation showed the Chancellor had lost the credibility to manage the economy in the interests of the majority of the people.
"The Chancellor has failed the British people. He should follow the honourable course taken by Iain Duncan Smith and resign," he said.
Prime Minister David Cameron said he was "puzzled and disappointed" by Duncan Smith's decision to resign as Work and Pensions Secretary.
