Chalfont resigned from the Labour Party in the early 1970s. He declared his resignation a "decision of personal and political principle". In October 1974, just after Labour won a second general election that year, he stated in an interview with the BBC journalist Robin Day: "I had hoped for a realignment of the politics of the radical left in this country and I believed when I left the Labour Party that a great success by the Liberal Party in this election could have helped that forward."