Kedgley was involved with student politics and was a member of the Victoria University of Wellington Students' Association from 1967–1969. In 1971 she stood for the Auckland City Council as a Labour Party candidate. Before entering national politics, Kedgley served on the Wellington City Council (WCC) for 7 years and was the founder and co-convenor of the New Zealand Safe Food Campaign. While on the WCC, Kedgley held the roles of Chairperson, Consultation Committee, 1996–1998 and Chairperson, Transport and Infrastructure Committee, 1998–1999.
Kedgley worked for the United Nations in New York for 8 years and for a decade as a television reporter, director and producer in New Zealand.
Kedgley has written a number of books on feminist issues, and was one of the founding leaders of the women's liberation movement in New Zealand. Her most recent book, titled Eating Safely in a Toxic World, has set the scene in New Zealand for a new movement of 'safe-food campaigners'.
Kedgley represented the Green Party in the Parliament of New Zealand since first becoming a Member of Parliament as a list MP in the 1999 elections until 2011. She won re-election in the 2002, 2005 and 2008 general elections. Particular political interests include health, food safety, animal welfare, consumer affairs, transport and women's issues.
In 2005 her Employment Relations (Flexible Working Arrangements) Amendment Bill, granting employees with dependants the right to request part-time or flexible hours, was drawn from the member's ballot. The bill was eventually passed as the Employment Relations (Flexible Working Arrangements) Amendment Act 2007.
In 2006 her Consumer's Right to Know (Food Information) Bill was drawn from the member's ballot, but was defeated at its first reading.
Kedgley was the Chairperson of the New Zealand Parliament Health Committee from 2005–2008 and was the Deputy Chair for 6 years prior.
In September 2010 she announced that she would not be standing for re-election in the 2011 general election. She gave her valedictory speech on 27 September.
In July 2013, Kedgley announced that she would be running for the Greater Wellington Regional Council on a Green Party ticket in the Wellington ward. She won a position on the Regional Council as well as the Capital and Coast District Health Board in the October elections.
As of 2017 Kedgley is the deputy chair of Consumer NZ and was first elected to the Board in 2013.
In 2016, Kedgley received the New Zealand Women of Influence Award for Diversity in recognition of her work towards greater gender diversity in the workplace.
She is married to Wellington lawyer and former Wellington City and Regional Councillor, Denis Foot, and they have one son, Zac.