Lees-Smith was from an Army family; his father was a Major in the Royal Artillery, and he was born in British India. He was educated at Aldenham School, as a cadet at the Royal Military Academy, Woolwich, and Queen's College, Oxford. Rejecting a military career, he chose academia and was appointed as a lecturer in Public Administration at the London School of Economics in 1906; he remained there throughout his political career. He was also Chairman of the Executive Committee of Ruskin College, Oxford, from 1907 to 1909. He resigned on appointment as Professor of Public Administration at the University of Bristol. In 1909 he went on an extended tour of India to lecture at Bombay on economics and advise on economics teaching; as a result of his experiences he wrote Studies in Indian Economics. He joined a territorial regiment in 1915, and was wounded as a stretcher beareron the Western Front and invalided out of the armed forces in 1917. In 1938 he distributed 40 British passports to German Jews in Frankfurt thus aiding their escape. The Chest of Surprises describes the Lees-Smith family history.
In 1919 Lees-Smith joined the Labour Party. He was picked as Labour candidate for Keighley and won the seat in the 1922 general election, profiting from a divided opposition. He was a noted speaker on banking and on reform of the House of Lords about which he wrote several books including Second Chambers in Theory and Practice. Unfortunately for Lees-Smith, the Conservatives stood down in the 1923 general election and he was defeated by the Liberal candidate. This defeat prevented him from being appointed as a Minister in the first Labour government.
Ministerial office
The collapse of the Liberal Party in the 1924 general election meant that Lees-Smith was able to win his seat back and he was swiftly appointed to a front-bench role. When Labour returned to office in 1929 he was made Postmaster-General where he defended the nationalised Post Office and tried to smarten up the Post Office counters. In a reshuffle in March 1931 he was promoted to President of the Board of Education and sworn of the Privy Council. In this capacity in June he gave the opening address at the Second International Congress of the History of Science. He had only a brief time in office before the government fell, and Lees-Smith refused to follow Ramsay MacDonald into the National Government. Defeated again in 1931, Lees-Smith again won his seat back in 1935. He served on the front bench but was not invited by Winston Churchill to join the Coalition government in 1940; as one of the most senior Labour figures not in office, the responsibilities of running the party were given to him. In his partisan role he strongly supported Churchill's conduct as war leader at a time when the war did not always run in the Allies' favour.