Dianne (Dee) Margetts was born in 1955 in Fremantle and educated locally. In 1979 she left Australia to study in the United Kingdom where she completed an Honours Degree in Development Studies at the University of East Anglia in 1982. She returned to Australia to complete a Diploma in Education at the University of Western Australia and was a teacher and librarian at high schools until 1988, when she became Coordinator for People for Nuclear Disarmament, a position she held until 1991.
In the 1989 state election, Dee stood as a candidate for the Alternation Coalition, a precursor to the Greens, in the seat of Fremantle. At the 1990 federal election, she stood as a Greens candidate for the seat of Swan. In 1991, Dee stood as a candidate for the mayor of Perth in the local government elections, earning 9.5% of the vote. She was the Economics spokesperson in The Greens (WA) from 1990 and Network Coordinator in The Greens (WA) in 1993.
In 1993 Dee was elected to the Senate. She and Christabel Chamarette were in balance of power from 1993 until Christabel lost her seat in 1996.
Dee lost her Senate seat at the 1998 federal election. Two weeks after completing her Senate term in mid-1999, she commenced her Masters Thesis on "Competition Policy, State Agreement Acts and the Public Interest" which was completed and approved in 2001.
In 2001 Dee was elected to the West Australian Legislative Council for the Agricultural region. While in the Council she was a member of the Standing Committee on Public Administration and Finance. She lost her seat at the 2005 state election.
Because of her concerns about the National Competition policy, which had been pushed through in Federal Parliament in 1994, Dee commenced her research for a PhD at University of WA (UWA) in early 2006. Her thesis "A Critique of Australia's National Competition Policy: Assessing its outcomes in a range of major sectors" was completed and approved in 2013.