Cardiff South and Penarth (Welsh: De Caerdydd a Phenarth) is a constituency created in 1983 represented in the House of Commons of the UK Parliament since 2012 by Stephen Doughty, a Labour Co-op MP.

[5] Prior to 1983 Penarth had been part of the abolished Barry constituency, represented by the Conservative backbencher Sir Raymond Gower.

Most of the electorate of the new constituency had previously fallen into the abolished seat of Cardiff South East, represented by former Prime Minister, James Callaghan.

Cardiff South and Penarth has had three MPs since its creation, containing some very safe Labour wards from Cardiff such as Butetown, Grangetown and Splott, and several wards from the neighbouring borough of the Vale of Glamorgan, with Penarth mostly favourable to Labour, but with some areas such as Plymouth and Sully in the southern end of the seat where the Conservatives attracted more support.

[6] Michael opted to drop the reference to the Co-operative Party but after the election denounced the ruling as "an outrageous piece of incompetence by the Electoral Commission".

[9][10] At a by-election held on 15 November 2012, Labour's decline was reversed coupled with very low turnout (down 38.2% on the previous election).