Labour MPs Stephen Doughty and Lucy Powell both tweeted they were "honoured" after their by-election victories.
Honoured and humbled to be elected as the new Labour and Coop MP for Cardiff South and Penarth!
Honoured and thrilled to be elected. Big vote for Labour and huge rejection of Tory-Lib Dem gov. Off to bed now #PuttingMCRFirst
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.