In 1771 Auckland published "Principles of Penal Law", and soon became a recognized authority on commercial and economic questions. In 1772 he took up an appointment as Under-Secretary of State for the North, a post he held until 1778. He was Member of Parliament for Woodstock from 1774 to 1784 and served as a Lord of Trade from 1776 to 1782. In 1778 he carried an Act for the improvement of the treatment of prisoners, and accompanied the Earl of Carlisle as a commissioner to North America on an unsuccessful mission to bring an end to the American War of Independence. During the War, he was head of the British spies in Europe, his budget reaching £200,000 by 1778. He probably oversaw a small group of intelligence collectors for Lord Suffolk. On his return in 1779 he published his widely-read "Four Letters to the Earl of Carlisle". In 1780 Auckland became Chief Secretary for Ireland, which he remained until 1782, and was admitted to the Irish Privy Council in 1780. He represented Dungannon in the Irish House of Commons between 1781 and 1783 and was Joint Vice-Treasurer of Ireland between 1783 and 1784. While in Ireland he established the National Bank.