Born in Lambeth, London to Irish parents, Kennedy grew up on the Aylesbury Estate in Southwark.

During the 1992 general election, in the constituency of Coventry South East, Kennedy worked on Jim Cunningham's campaign and helped narrowly defeat Militant-affiliated MP Dave Nellist, who had been deselected as Labour's candidate.

Kennedy was made a life peer in the 2010 Dissolution Honours on the recommendation of Gordon Brown, the outgoing prime minister.

Kennedy returned to the role in September 2015, under the leadership of Jeremy Corbyn, and was also appointed as a shadow spokesperson for Communities and Local Government, Housing and Home Affairs.

As Opposition Chief Whip, he became Deputy Chair of the Lords Committees and a shadow cabinet attendee, now under the leadership of Sir Keir Starmer.