Iain Duncan Smith, the former Work and Pensions Secretary, has told ITV News he had no choice but to resign in order to push the government into pursuing a fairer welfare policy.
Speaking to ITV News' political editor Robert Peston, Mr Duncan Smith said his department was under enormous pressure to meet arbitrary targets which unfairly placed the burden on struggling working people and the vulnerable.
The former minister resigned on Friday evening saying that pairing back disability benefit while offering tax cuts to the better off was "a compromise too far".
"I think I can't do this any longer inside, I have to go out, resign and argue for this kind of process outside," he said.
That told me something, that the direction of travel was now getting narrower, and that we were really in a search solely for money and we were beginning to forget that actually the wider nature of governing as one nation and wanting to help people to help themselves, we would lose that because we wouldn't practically be able to do it.
Mr Duncan Smith called suggestions he had resigned to campaign for Britain to leave the European Union "Machiavellian".
"If I was that clever and intelligent I would be incredibly proud of an assertion that was completely wrong," he said.
"My resignation note was straightforward."
I have been in government for one sole purpose, I have no other ambitions, I was simply caring about the idea that we try and find a way to for the Conservatives to implement social justice. As we balance the economy, so we must balance society, and that seems to be the best way to do it and I care about that enormously and that's the reason I am going. It has nothing to do with Europe.
Prime Minister David Cameron has said he was "puzzled and disappointed" by Mr Duncan Smith's decision to resign.