The former head of the Conservative Party from 2001 to 2003 will take over the role previously held by Labour MP Yvette Cooper.
Duncan Smith is a former army officer who served in Northern Ireland. He was shadow defence secretary when William Hague (who has just been appointed foreign secretary) was leader of the Tories.
In his role Duncan Smith will be responsible for pension policy (including the implementation of the NEST scheme and auto-enrolment by 2012) as well as JobcentrePlus and unemployment.
