| Macclesfield | England | E14001347 |
| Maidenhead | England | E14001348 |
| Maidstone and Malling | England | E14001349 |
| Makerfield | England | E14001350 |
| Maldon | England | E14001351 |
| Manchester Central | England | E14001352 |
| Manchester Rusholme | England | E14001353 |
| Manchester Withington | England | E14001354 |
| Mansfield | England | E14001355 |
| Melksham and Devizes | England | E14001356 |
| Melton and Syston | England | E14001357 |
| Meriden and Solihull East | England | E14001358 |
| Merthyr Tydfil and Aberdare | Wales | W07000099 |
| Mid and South Pembrokeshire | Wales | W07000100 |
| Mid Bedfordshire | England | E14001359 |
| Mid Buckinghamshire | England | E14001360 |
| Mid Cheshire | England | E14001361 |
| Mid Derbyshire | England | E14001362 |
| Mid Dorset and North Poole | England | E14001363 |
| Mid Dunbartonshire | Scotland | S14000097 |
| Mid Leicestershire | England | E14001364 |
| Mid Norfolk | England | E14001365 |
| Mid Sussex | England | E14001366 |
| Mid Ulster | Northern Ireland | N05000010 |
| Middlesbrough and Thornaby East | England | E14001367 |
| Middlesbrough South and East Cleveland | England | E14001368 |
| Midlothian | Scotland | S14000045 |
| Milton Keynes Central | England | E14001369 |
| Milton Keynes North | England | E14001370 |
| Mitcham and Morden | England | E14001371 |
| Monmouthshire | Wales | W07000101 |
| Montgomeryshire and Glyndwr | Wales | W07000102 |
| Moray West, Nairn and Strathspey | Scotland | S14000098 |
| Morecambe and Lunesdale | England | E14001372 |
| Motherwell, Wishaw and Carluke | Scotland | S14000099 |