(Click on the column title to sort by that column)
| # | Catholics | Population | Percent Catholic | Diocese | Year | Source |
|---|---|---|---|---|---|---|
| 1 | 506,319 | 1,100,000 | 46.03% | Liverpool (Archdiocese) | 2004 | ap2005 |
| 2 | 465,587 | 4,613,284 | 10.09% | Westminster (Archdiocese) | 2004 | ap2005 |
| 3 | 385,384 | 4,048,900 | 9.52% | Southwark (Archdiocese) | 2004 | ap2005* |
| 4 | 287,717 | 2,208,000 | 13.03% | Salford | 2004 | ap2005 |
| 5 | 286,500 | 5,245,000 | 5.46% | Birmingham (Archdiocese) | 2004 | ap2005 |
| 6 | 234,617 | 1,838,000 | 12.76% | Shrewsbury | 2004 | ap2005 |
| 7 | 224,344 | 779,490 | 28.78% | Glasgow (Archdiocese) | 2003 | ap2004 |
| 8 | 222,719 | 2,710,000 | 8.22% | Brentwood | 2004 | ap2005 |
| 9 | 219,314 | 2,241,491 | 9.78% | Hexham and Newcastle | 2004 | ap2005 |
| 10 | 173,539 | 2,000,769 | 8.67% | Northampton | 2004 | ap2005 |
| 11 | 167,632 | 2,960,077 | 5.66% | Portsmouth | 2004 | ap2005 |
| 12 | 165,100 | 633,000 | 26.08% | Motherwell | 2004 | ap2005 |
| 13 | 154,957 | 2,000,000 | 7.75% | Leeds | 2004 | ap2005 |
| 14 | 146,672 | 3,000,000 | 4.89% | Arundel and Brighton | 2004 | ap2005 |
| 15 | 134,470 | 3,609,000 | 3.73% | Nottingham | 2004 | ap2005 |
| 16 | 133,944 | 1,956,166 | 6.85% | Clifton | 2003 | ap2004 |
| 17 | 117,000 | 2,755,000 | 4.25% | East Anglia | 2004 | ap2005 |
| 18 | 112,978 | 1,434,347 | 7.88% | Saint Andrews and Edinburgh (Archdiocese) | 2004 | ap2005 |
| 19 | 111,264 | 1,050,000 | 10.60% | Lancaster | 2004 | ap2005 |
| 20 | 86,536 | 1,398,203 | 6.19% | Cardiff (Archdiocese) | 2004 | ap2005 |
| 21 | 81,995 | 1,134,000 | 7.23% | Middlesbrough | 2004 | ap2005 |
| 22 | 79,400 | 342,000 | 23.22% | Paisley | 2004 | ap2005 |
| 23 | 66,000 | 1,500,000 | 4.40% | Hallam | 2004 | ap2005 |
| 24 | 53,679 | 2,548,200 | 2.11% | Plymouth | 2004 | ap2005 |
| 25 | 47,856 | 520,000 | 9.20% | Galloway | 2004 | ap2005 |
| 26 | 43,000 | 400,000 | 10.75% | Dunkeld | 2004 | ap2005 |
| 27 | 30,272 | 692,800 | 4.37% | Wrexham | 2004 | ap2005 |
| 28 | 26,266 | 788,550 | 3.33% | Menevia | 2004 | ap2005 |
| 29 | 15,000 | Great Britain, Faithful of Eastern Rite (Ukrainian) (Apostolic Exarchate) | 2002 | ap2003 | ||
| 30 | 11,173 | 700,000 | 1.60% | Aberdeen | 2004 | ap2005 |
| 31 | 10,434 | 75,000 | 13.91% | Argyll and the Isles | 2004 | ap2005 |
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