In 2015, Steen served as special envoy to the prime minister and to Parliament's Joint Select Committee on the draft Modern Slavery Bill. In February 2016, Steen and Baron Randall of Uxbridge (then Sir John Randall MP) were appointed special envoys on modern slavery to the mayor of London. In October 2018, Steen was appointed a specialist adviser, representing NGOs and civil society, on a review into the operation of the Modern Slavery Act. In November 2018, he was appointed specialist adviser on modern slavery to the Home Affairs Select Committee in the House of Commons.
