Kennedy was the Labour Member of Parliament (MP) for Liverpool Broadgreen from 1992 until 1997 and for Liverpool Wavertree from 1997 until the 2010 general election.
Formerly a member of the Government, on 8 June 2009, she returned to the backbenches leaving her position as Minister of State for Farming and the Environment at the Department for Environment, Food and Rural Affairs.She left the Labour Party in early 2019 after the resignation of Luciana Berger MP, and the announcement that Derek Hatton had been re-admitted to party membership.