 Elected as a councillor in 1992 on Brighton Borough Council, Kirby later also served on Mid Sussex District Council and East Sussex County Council, where he was the cabinet member with responsibility for economic development.He stood down as a councillor in 2009 to concentrate on winning the parliamentary seat of Brighton Kemptown.He was elected to the House of Commons as MP for Brighton, Kemptown in the May 2010 general election, with a majority of 1,328, gaining the seat from Labour.