Cameron told MPs this afternoon that he is committed to "compassionate conservatism" after Duncan Smith left his role as work and pensions secretary over what he called a deeply unfair Budget.
Duncan Smith was drawing attention in particular to planned disability cuts, something that had caused controversy on all sides of the House of Commons. Newly promoted Stephen Crabb today confirmed that planned cuts to personal independence payments had been scrapped, in his first statement to MPs as work and pensions secretary.
Cameron said over the weekend that he was "puzzled and disappointed" at Duncan Smith's departure.
The resignation comes after it was reported that Tory backbenchers would rebel against the government on the issue of disability benefits.
Number 10 has also ardently denied reports of a row between Cameron and chancellor George Osborne following the resignation. However, Cameron today stressed his support for Osborne, and credited him with "turning the economy around".
Following the ill-received Budget Osborne became less likely to become the next Conservative party leader.