At-a-glance: The Tory row over reforms to disability benefit
Iain Duncan Smith's resignation has led to Tory civil war - but what caused the controversy?
The resignation of work and pensions secretary Iain Duncan Smith has opened a deep rift within the Conservatives.
But the catalyst for the minister's decision was a proposed cut to the Personal Independence Payment (PIP), which helps those with long-term disabilities.
But what is PIP and why is it so controversial?