Labour have held on to the parliamentary seat of Cardiff South and Penarth in the by-election.
Stephen Doughty, who has previously been the head of Oxfam Cymru, will be the new MP.
Labour has held the seat since 1945.
For more on the by-election, visit ITV Wales.
Ed Miliband claimed that Middle England was turning its back on David Cameron, after Labour won the Corby by-election on a 12.7% swing.
Labour today held Manchester Central and Cardiff South and Penarth constituency seats in their respective by-elections.