With thanks to Graham King of UK General Election 2015 for sourcing the information.

We would add that quite a few of the seats below are also potential UKIP target seats, such as Camborne and Redruth and Thurrock.

# Labour targets Swing required Conservative   Targets Swing required Liberal   Democrat targets Swing required
1 North   Warwickshire (CON) 0.05% Hampstead   and Kilburn (LAB) 0.04% Camborne   and Redruth (CON) 0.08%
2 Thurrock   (CON) 0.10% Bolton   West (LAB) 0.10% Oldham   East and Saddleworth (LAB) 0.12%
3 Hendon   (CON) 0.12% Solihull   (LD) 0.16% Oxford   West and Abingdon (CON) 0.16%
4 Cardiff   North (CON) 0.20% Southampton   Itchen (LAB) 0.22% Ashfield   (LAB) 0.20%
5 Sherwood   (CON) 0.22% Dorset   Mid and Poole North (LD) 0.29% Sheffield   Central (LAB) 0.20%
6 Norwich   South (LD) 0.32% Wirral   South (LAB) 0.66% Edinburgh   South (LAB) 0.36%
7 Stockton   South (CON) 0.33% Derby   North (LAB) 0.68% Truro   and Falmouth (CON) 0.45%
8 Broxtowe   (CON) 0.37% Wells   (LD) 0.72% Newton   Abbot (CON) 0.55%
9 Lancaster   and Fleetwood (CON) 0.39% Dudley   North (LAB) 0.84% Chesterfield   (LAB) 0.60%
10 Bradford   East (LD) 0.45% Great   Grimsby (LAB) 1.08% Swansea   West (LAB) 0.71%
11 Amber   Valley (CON) 0.58% Morley   and Outwood (LAB) 1.13% Hull   North (LAB) 0.96%
12 Waveney   (CON) 0.75% Telford   (LAB) 1.19% Rochdale   (LAB) 0.97%
13 Wolverhampton   South West (CON) 0.85% Walsall   North (LAB) 1.37% Harrogate   and Knaresborough (CON) 0.98%
14 Morecambe   and Lunsdale (CON) 1.00% St.   Austell and Newquay (LD) 1.39% Watford   (CON) 1.29%
15 Carlisle   (CON) 1.01% Somerton   and Frome (LD) 1.50% Hampstead   and Kilburn (LAB) 1.51%
16 Stroud   (CON) 1.12% Birmingham   Edgbaston (LAB) 1.54% Montgomeryshire   (CON) 1.75%
17 Weaver   Vale (CON) 1.13% Sutton   and Cheam (LD) 1.66% Edinburgh   North and Leith (LAB) 1.82%
18 Lincoln   (CON) 1.16% Halifax   (LAB) 1.69% St.   Albans (CON) 2.19%
19 Brighton   Pavilion (Green) 1.21% Newcastle-under-Lyme   (LAB) 1.80% Newport   East (LAB) 2.39%
20 Plymouth   Sutton and Devonport (CON) 1.31% Middlesbrough   South and East Cleveland (LAB) 1.82% Weston-super-Mare   (CON) 2.56%
21 Dewsbury   (CON) 1.41% Wakefield   (LAB) 1.82% Hereford   and Herefordshire South (CON) 2.57%
22 Warrington   South (CON) 1.42% St.   Ives (LD) 1.87% Devon   West & Torridge (CON) 2.68%
23 Brent   Central (LD) 1.48% Plymouth   Moor View (LAB) 1.91% Winchester   (CON) 2.73%
24 Bedford   (CON) 1.50% Gedling   (LAB) 1.93% Northampton   North (CON) 3.09%
25 Brighton   Kemptown (CON) 1.56% Eltham   (LAB) 1.98% Cornwall   South East (CON) 3.25%
26 Pudsey   (CON) 1.69% Walsall   South (LAB) 2.15% Bristol   North West (CON) 3.25%
27 Brentford   and Isleworth (CON) 1.82% Nottingham   South (LAB) 2.17% City of Durham (LAB) 3.32%