| Longford (1918 - 1922) |
Constituency of same name also existed 1832-1885. |
| Lonsdale (1918 - 1950) |
Full name (in Craig 3) Lancashire, Lonsdale |
| Louth [county, Ireland] (1918 - 1922) |
Constituency of same name also existed 1832-1885. |
| Manchester, Ardwick (1918 - 1983) |
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| Manchester, Blackley (1918 - 2010) |
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| Manchester, Clayton (1918 - 1955) |
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| Manchester, Exchange (1918 - 1974) |
Constituency first used at the February General election of 1974 (28/02/1974). |
| Manchester, Gorton (1918 - 2024) |
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| Manchester, Hulme (1918 - 1950) |
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| Manchester, Moss Side (1918 - 1983) |
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| Manchester, Platting (1918 - 1950) |
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| Manchester, Rusholme (1918 - 1950) |
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| Manchester, Withington (1918) |
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| Merthyr Tydfil Aberdare (1918 - 1950) |
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| Merthyr Tydfil Merthyr (1918 - 1950) |
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| Middlesbrough East (1918 - 1974) |
Constituency first used at the February General election of 1974 (28/02/1974). |
| Middlesbrough West (1918 - 1974) |
Constituency first used at the February General election of 1974 (28/02/1974). |
| Middleton and Prestwich (1918 - 1983) |
Full name (in Craig 3,4) Lancashire, Middleton and Prestwich |
| Midlothian and Peeblesshire Northern (1918 - 1950) |
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| Mitcham (1918 - 1974) |
Constituency first used at the February General election of 1974 (28/02/1974). Full name (in Craig 3) Surrey, Mitcham. Craig (3) 188 from 1945 revision. |
| Monmouth (1918 - 2024) |
Full name (in Craig 3,4) Monmouthshire, Monmouth |
| Moray and Nairnshire (1918 - 1974) |
Constituency first used at the February General election of 1974 (28/02/1974). 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 (1974ยน-1983). |
| Mossley (1918 - 1950) |
Full name (in Craig 3) Lancashire, Mossley |
| Motherwell (1918 - 1974) |
Constituency first used at the February General election of 1974 (28/02/1974). Full name (in Craig 3,4) Lanarkshire, Motherwell |
| National University (1918 - 1922) |
Non-geographic constituency. |