A very odd state of affairs recounted in Bruce Moore’s Speaking our Language: The Story of Australian English:

In 1949, Labor Prime Minister Chifley, in the Nationality and Citizenship Act, created the term ‘Australian citizen’ (prior to this Australians were merely British subjects), and created an Australian passport to replace the British passport that Australians until then had carried on overseas travel. In 1949, incoming Liberal Prime Minister Menzies revoked the Australian passport, and until 1973 Australians continued to carry a passport labelled ‘British passport’.