Chancellor George Osborne has said that he is "sorry" that former work and pensions secretary Iain Duncan Smith resigned after last week's Budget and that he is prepared to "listen and learn" from his mistakes.
Addressing MPs in the House of Commons earlier today, Osborne said: "I am sorry that my right honourable friend chose to leave the government."
But the chancellor added he was "very proud" of his years working with Duncan Smith, saying: "Let me here in this House recognise his achievements in helping to make work pay, protecting the vulnerable and breaking the decades-old cycle of welfare dependency."
Duncan Smith, a former Conservative party leader who was first appointed as work and pensions secretary in 2010, resigned at the end of last week, citing concerns over Osborne's proposals to cut disability benefits.
"There is always robust discussion between the Treasury and the spending departments when money needs to be saved," Osborne told MPs today, in a nod to persistent disagreements between him and Duncan Smith.
"The decisions we made to keep our economy secure are always difficult," Osborne added. "And where we don't get them right, I have always been prepared to listen and learn.
"But I am very proud that my right honourable friend and I worked together longer than any two people doing our jobs before us in any government."
The chancellor used his statement in the Commons to defend last week's Budget, despite confirming that the proposed disability benefit cuts will not go ahead, leaving a £4.4bn black hole in the spending plans.
Labour MPs pushed Osborne to explain how he will cover the gap.
The Budget has taken its toll on the Osborne's popularity, with bookmakers extending his odds of taking over from Cameron at the end of this parliament and a new YouGov poll finding just eight per cent of people think the chancellor is up for the job of Prime Minister.
William Hill have now even shortened the odds of Osborne standing down before the end of the year from 6/1 to 7/4.
"This is the most difficult situation the Chancellor has been in since taking on the job and thee are plenty of political punters betting that it will herald his departure from the role sooner rather than later" said Hill's spokesman Graham Sharpe.
And in the latest chapter in battle for the Tory leadership, Boris Johnson said Osborne's proposed disability cuts were "a mistake".