| Monaghan North |
|
| Monaghan South |
|
| Monklands East |
|
| Monklands West |
|
| Monmouth |
Full name (in Craig 3,4) Monmouthshire, Monmouth |
| Monmouth District of Boroughs |
|
| Monmouthshire |
|
| Monmouthshire Northern |
|
| Monmouthshire Southern |
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| Monmouthshire Western |
|
| Montgomery |
|
| Montgomery District of Boroughs |
|
| Montgomeryshire |
Constituency of same name reformed 1997. |
| Montgomeryshire |
Constituency of same name also existed 1832-1974¹. |
| Montrose District of Burghs |
|
| Moray |
|
| Moray and Nairn |
Probably not a true founding in 1974 - may be simply a difference of nomenclature between Craig and Times HoC sources. See also Moray and Nairnshire (1918-1974¹). |
| Moray and Nairnshire |
Probably not a true disbandment in 1974 - may be simply a difference of nomenclature between Craig and Times HoC sources. See also Moray and Nairn (1974¹-1983). |
| Morecambe and Lonsdale |
Full name (in Craig 4) Lancashire, Morecambe and Lonsdale |
| Morecambe and Lunesdale |
|