He stood for Parliament as a Liberal in 1910 and 1929. Hirst campaigned against the post-war revival of protectionism under the guise of safeguarding. In 1927 he noted the Labour Party's opposition to tariffs but also doubted whether "any system of socialism is ultimately compatible with the policy of free imports and the open door". When the Liberal Walter Runciman, President of the Board of Trade, introduced the Abnormal Importations (Customs Duties) Act 1931 Hirst accused Runciman of pursuing a "Tariff of Abominations, the worst since Waterloo", with the Ottawa Agreement meaning that Britain's tariff policy was no longer under the control of the British Parliament but by the colonies. It was an inversion of George III's policy in regard to the American colonies: "It is now the turn of the Colonies to control the mother country's taxes!"