Notional results for a UK general election on 5 May 2005 Wales - by majority
| Constituency | Winning party | Valid votes | Majority (votes) | Majority (%) |
| Rhondda | Lab | 31,148 | 16,242 | 52.1% |
| Islwyn | Lab | 33,871 | 17,582 | 51.9% |
| Cynon Valley | Lab | 29,080 | 14,390 | 49.5% |
| Merthyr Tydfil and Rhymney | Lab | 29,976 | 13,934 | 46.5% |
| Aberavon | Lab | 30,104 | 13,937 | 46.3% |
| Ogmore | Lab | 32,059 | 14,839 | 46.3% |
| Torfaen | Lab | 35,979 | 14,791 | 41.1% |
| Caerphilly | Lab | 36,223 | 13,517 | 37.3% |
| Swansea East | Lab | 30,834 | 11,249 | 36.5% |
| Neath | Lab | 35,817 | 12,710 | 35.5% |
| Pontypridd | Lab | 34,184 | 11,694 | 34.2% |
| Dwyfor Meirionnydd | PC | 29,996 | 8,706 | 29.0% |
| Blaenau Gwent | Ind | 35,251 | 9,121 | 25.9% |
| Alyn and Deeside | Lab | 35,496 | 8,378 | 23.6% |
| Montgomeryshire | LD | 30,914 | 7,048 | 22.8% |
| Cardiff South and Penarth | Lab | 39,487 | 8,955 | 22.7% |
| Wrexham | Lab | 30,385 | 6,819 | 22.4% |
| Cardiff West | Lab | 37,578 | 8,361 | 22.2% |
| Newport East | Lab | 31,825 | 6,838 | 21.5% |
| Llanelli | Lab | 35,344 | 7,234 | 20.5% |
| Clwyd South | Lab | 31,350 | 6,220 | 19.8% |
| Delyn | Lab | 34,004 | 6,644 | 19.5% |
| Bridgend | Lab | 34,079 | 6,089 | 17.9% |
| Carmarthen East and Dinefwr | PC | 37,344 | 6,551 | 17.5% |
| Gower | Lab | 39,542 | 6,703 | 17.0% |
| Cardiff Central | LD | 36,132 | 5,593 | 15.5% |
| Newport West | Lab | 35,732 | 5,458 | 15.3% |
| Vale of Clwyd | Lab | 32,644 | 4,629 | 14.2% |
| Swansea West | Lab | 33,086 | 4,269 | 12.9% |
| Brecon and Radnorshire | LD | 38,341 | 3,905 | 10.2% |
| Monmouth | Con | 45,653 | 4,527 | 9.9% |
| Carmarthen West and South Pembrokeshire | Lab | 38,429 | 2,043 | 5.3% |
| Aberconwy | Lab | 27,258 | 1,070 | 3.9% |
| Ynys Môn | Lab | 35,462 | 1,242 | 3.5% |
| Vale of Glamorgan | Lab | 46,748 | 1,574 | 3.4% |
| Cardiff North | Lab | 45,360 | 1,146 | 2.5% |
| Arfon | Lab | 25,042 | 456 | 1.8% |
| Preseli Pembrokeshire | Con | 39,199 | 601 | 1.5% |
| Ceredigion | LD | 35,716 | 218 | 0.6% |
| Clwyd West | Con | 36,047 | 51 | 0.1% |
Estimates of the 2005 general election result in new constituencies
Colin Rallings and Michael Thrasher, then at the University of Plymouth, produced estimates of the 2005 general election result as if the new constituencies recommended by the separate Parliamentary Boundary Commissions for England, Wales and Northern Ireland had then been in existence.
The Elections Centre, established by Professors Colin Rallings and Michael Thrasher, moved to the University of Exeter in 2003.