Leith-Ross was born in Mauritius, but grew up with his grandfather at the family estate, Arnage Castle in Scotland. His father, Frederick William Arbuthnot Leith-Ross, was a banker while his Dutch mother was the daughter of a prominent politician. He was the brother of the artist Harry Leith-Ross (1886–1973). After graduating with a double first from Balliol College, Oxford, he joined the Treasury in 1909.
Leith-Ross was appointed as a Private Secretary to H. H. Asquith, the prime minister, in 1911. Between 1932 and 1945 he was chief economic advisor to the UK government: he is known for advancing the economic theory of "Treasury View", popular in the 1930s. Leith-Ross was active in negotiations with Germany prior to the Second World War but is best remembered for the "Leith-Ross mission" to China in 1935, when he was the UK's chief representative in a mission to persuade China to reform its currency. He was also chairman of a bank in China and chairman of P&O.
During the Second World War, Leith-Ross helped to lay the foundation for international humanitarian relief efforts in the postwar period. Following a speech of prime minister Winston Churchill to the British Parliament on 20 August 1940 that rhetorically raised the prospect of Britain bringing the German and Austrian peoples "food, freedom, and peace" upon the defeat of the Nazi regime in Europe, Leith-Ross was appointed to head an ad hoc governmental committee to address the question of how surpluses could be raised to deliver on such a pledge. In September 1941, his committee was reconstituted as the Inter-Allied Committee on Post-War Requirements, in which form it collaborated with the European governments in exile in London, on estimating the needs for food, raw materials, and other necessities in the first six-month period after liberation.
Leith-Ross's committee laid the groundwork for what eventually became the United Nations Relief and Rehabilitation Administration (UNRRA), founded in November 1943. As deputy under the UNRRA's first director-general, the American Herbert Lehman, Leith-Ross contributed to the difficult work of organizing and staffing the new international agency, which, in the end, received the mandate not of feeding German civilians but, rather, of fulfilling basic needs of the millions of people displaced from their homelands as a consequence of the war, who needed assistance to be repatriated or to otherwise re-establish their lives in the postwar period. The term displaced persons, which came into parlance at that time, and shaped the understanding of the postwar landscape, may have even originated in Leith-Ross's committee and the report it produced.
In 1912 Leith-Ross married Prudence Staples. Their children include the author Prudence Leith-Ross. His 1968 autobiography is entitled Money Talks: Fifty years of international finance.
- Middleton, Roger (2004). "Ross, Sir Frederick William Leith- (1887–1968)". Oxford Dictionary of National Biography. Oxford University Press. doi:10.1093/ref:odnb/34489.(subscription or UK public library membership required)
- A History of Modern Shanghai Banking, Zhaojin Ji, 2002
- Shanghai's Bund and Beyond, Niv Horesh, Yale University Press, 2009
- Shephard, Ben. The Long Road Home: The Aftermath of the Second World War. New York: Knopf, 2011. 33-34.
- Shephard, 35.
- Shephard, 56, 59.
- Shephard, 38-39, 51-52.