When the Conservatives entered into a coalition with the Liberal government in 1915, Chaplin became the leader of an Opposition in the House of Commons that offered friendly criticism. He held his seat in the Commons until 1916, when he was raised to the peerage as Viscount Chaplin, of Saint Oswald's, Blankney, in the County of Lincoln. He believed that the emergency wartime measures taken by the government to ensure the supply of food had vindicated his protectionist beliefs, writing in April 1917 of "the vital need to go back to the old system and grow most of our food here in the future".