Iain Duncan Smith has dramatically quit the Cabinet, branding cuts to benefits for the disabled in George Osborne's Budget "indefensible".
In an excoriating parting shot at the Chancellor, the Work and Pensions Secretary complained of pressure to "salami slice" welfare and a failure to spread the burden of spending curbs.
"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," Mr 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. 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."