During the 1930's Priestley became very concerned about the consequences of social inequality in Britain, and in 1942 Priestley and others set up a new political party, the Common Wealth Party, which argued for public ownership of land, greater democracy, and a new 'morality' in politics. The party merged with the Labour Party in 1945, but Priestley was influential in developing the idea of the Welfare State which began to be put into place at the end of the war.
He believed that further world wars could only be avoided through cooperation and mutual respect between countries, and so became active in the early movement for a United Nations. And as the nuclear arms race between West and East began in the 1950s, he helped to found CND, hoping that Britain would set an example to the world by a moral act of nuclear disarmament.