The Government is to formally drop its cuts to disabled benefits after Iain Duncan Smith's dramatic resignation.
New Work and Pensions Secretary Stephen Crabb will tell the Commons in a statement that the curbs to the Personal Independence Payment (PIP) have been abandoned.
Prime Minister David Cameron is likely to be challenged over the situation when he addresses MPs about last week's Brussels summit on the migrant crisis.
The developments come after a day of Tory infighting that saw Mr Duncan Smith condemn Chancellor George Osborne's "arbitrary" cap on welfare spending and obsession with "short-term savings".
In a round of interviews, the former Conservative leader insisted his decision to quit the Cabinet was not "personal" or a "secondary attack" on the Prime Minister over Europe.
He said he felt the party was undermining its "one nation" ambitions by balancing the books on the back of the working age poor and vulnerable. The final trigger for his resignation was learning that Mr Osborne had "juxtaposed" the £1.3 billion a year PIP curbs with tax cuts for the better off in the Budget.
"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," Mr Duncan Smith 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."
Mr Duncan Smith flatly denied that his decision had anything to do with personal animosity to Mr Osborne or his desire for Britain to leave the EU, describing that as "the most puerile idea I have ever heard".
Energy Secretary Amber Rudd told Sky News's 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 of trying to inflict "maximum damage" on the party leadership to get Britain out of the EU.
But colleagues Priti Patel, Justin Tomlinson and Shailesh Vara 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 ... we'll see in the weeks and months ahead," she told the BBC's Sunday Politics.
Shadow chancellor John McDonnell insisted Mr Osborne 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.
Labour is likely to table an urgent question in a bid to force the Chancellor to come to the Commons.