British politician who was leader of the Conservative Party from 2001 to 2003.

Duncan Smith, whose father was a Royal Air Force (Royal Air Force, The) pilot during World War II, was educated privately, and for a period he attended HMS Conway, a school in Wales where the sons of officers were brought up in spartan conditions. In 1975 he entered army training at the Royal Military Academy, Sandhurst, and was subsequently commissioned into the Scots Guards; he rose to the rank of captain in 1979. In 1981 he decided that his future lay in civilian life, and he joined the defense electronics company GEC-Marconi as a sales and marketing executive—a role that took him frequently to the United States, where he forged links with Pentagon officials and Republican (Republican Party) politicians. In 1982 he married Elizabeth Wynne Fremantle, daughter of the 5th Baron Cottesloe.

In 1992 Duncan Smith entered the House of Commons as MP for Chingford and Woodford Green, strongly Conservative middle-class suburbs on the outskirts of London. He quickly established himself as a member of an anti- European Union group of Conservative backbench MPs who attacked their own party's government for signing the EU's Maastricht Treaty and who frequently voted against the government on European issues. He also established himself as a right-winger on other issues, most notably by arguing that the role of the state should be curbed significantly and that taxes should be sharply reduced.

When the Conservatives lost power in 1997, the party's new leader, William Hague, appointed Duncan Smith to his shadow cabinet, first as the party's official spokesman on social security. He became shadow defense secretary in 1999, but he continued to be known best for his uncompromising views on Europe. When Hague resigned following the party's disastrous performance in the general election held on June 7, 2001, Duncan Smith stood for the party leadership, promising that he would never support the entry of Britain into the EU's single currency. In the final runoff against his pro-European (and far more experienced) rival, Kenneth Clarke, Duncan Smith's views proved to be more in tune with the party membership, and he won 61 percent of the votes cast. His victory was all the more remarkable for the fact that he alone among the five candidates had never before served as a government minister.

Soon after becoming Conservative leader, however, Duncan Smith faced dwindling support within the party, as members questioned his ability to defeat Prime Minister Tony Blair (Blair, Tony) and the Labour Party in the next general election. In October 2003 he lost a no-confidence vote, and on November 6 he was replaced as head of the Conservative Party by Michael Howard. In 2004 Duncan Smith established the Centre for Social Justice, a think tank aimed at eliminating poverty.