Iain Duncan Smith has delivered a devastating assault on the Government's austerity drive, accusing David Cameron and George Osborne of balancing the books on the backs of poor and vulnerable working people.
As Tory infighting spiralled out of control in the wake of his dramatic resignation, the former work and pensions secretary condemned the Chancellor's "arbitrary" cap on welfare spending and obsession with "short term savings".
Energy Secretary Amber Rudd immediately lashed out at Mr Duncan Smith's "high moral tone" and dismissed the critique as "completely wrong". Meanwhile, ministers at his old department clashed openly after Baroness Altmann accused him of causing "maximum damage" in order to get Britain out of the EU.
Speaking on the BBC's Andrew Marr show, the former Conservative leader insisted his decision to quit was not "personal" or a "secondary attack" on the Prime Minister.
He said he felt the Conservatives were abandoning their "one nation" approach and there was "massive pressure" to finalise deep cuts to Personal Independence Payments (PIP) before the Budget.
Mr Duncan Smith said he finally chose to go after finding out that Mr Osborne had "juxtaposed" the £1.3 billion a year PIP curbs with tax cuts for the better off.
"The truth is yes, we need to get the deficit down, but we need to make sure we widen the scope of where we look to get that deficit down and not just narrow it down on working age benefits," he said.
"Because otherwise it just looks like we see this as a pot of money, that it doesn't matter because they don't vote for us."
Asked why he decided to quit even though the Treasury had signalled a last-minute climbdown on the PIP issue, Mr Duncan Smith said the department would still have been forced to find equivalent savings.
He also confirmed he considered resigning a year ago after a series of spats with the Chancellor over cuts to tax credits and his flagship Universal Credit project, which is merging working age benefits and aims to ensure people are always better off in work.
"This has been a long running problem when I have felt really semi-detached in a sense, isolated more often in these debates because I am not able to convince people that what we were losing progressively ... was the narrative that the Conservative Party was this one nation party caring about those who don't even necessarily vote for it, who may never vote for it," he said.
He flatly denied that his decision had anything to do with personal animosity to Mr Osborne or his desire for Britain to leave the EU, telling Sky News that was "the most puerile idea I have ever heard".
Ms Rudd told Sky News' Murnaghan programme she had "respect" for Mr Duncan Smith but his behaviour was "really disappointing".
"I do resent his high moral tone on that when the rest of us are absolutely committed to a one nation government," she said. "I do find his manner and his approach really disappointing."
Pensions minister Lady Altmann accused her old boss of "shocking" behaviour and trying to inflict "maximum damage" on the party leadership to get Britain out of the EU.
"I simply cannot understand why he suddenly chose to quit like this when it was clear that Number 10 and the Treasury had told him they were going to pause and rethink these measures. I'm particularly saddened that this really seems to be about the European referendum campaign rather than about DWP policy," she said.
But colleagues Priti Patel, Justin Tomlinson and Shailesh Vara lined up to hit back at Lady Altmann.
Employment minister Ms Patel told BBC radio 5 Live's Pienaar's Politics the departure was "not about Europe".
"With respect to Ros ... what I would like to say is that working with Iain he has always provided support and encouragement in all that we have done as a ministerial team," she said.
Tory backbencher Heidi Allen questioned whether Mr Osborne should continue as Chancellor. "It depends how he responds to that challenge. I'm hoping so, but we'll see in the weeks and months ahead," she told the BBC's Sunday Politics.
Shadow chancellor John McDonnell insisted Mr Osborne now had to "rip up" the financial package. "George Osborne needs to come back to Parliament now, pull this Budget and start again because this Budget isn't sustainable any more," he told BBC radio 5 live.