In 1911 he moved to the land tax branch of the Treasury, where he employed the young John McEwen (later Prime Minister) as a clerk.

B. Chifley than to their predecessors, Whitlam was largely responsible for preparing the documentation for the 1944 referendum on Commonwealth powers and, with the solicitor-general, for advising H. V. Evatt during the bank nationalisation litigation (1947–49).

In 1933 he led a campaign against Canberra residents being required to pay a hospital tax when they had no elected local government and no parliamentary representation.

"In the Australian context they would vote Labor as the party of change and public responsibility – things being done by elected persons rather than by self-perpetuating directorates.

As a member of the Australian delegation to the Paris Peace Conference in 1946, Whitlam argued Australia's case for a permanent international human-rights court, an idea whose time was yet to come.

Whitlam retired as Crown Solicitor in April 1949, but continued to be closely involved in United Nations matters as an adviser to the Department of External Affairs.