UK Polling Report has completed an initial review of the English boundary changes which predicts that “the provisional English boundaries would reduce the number of Conservative seats by 5, the number of Liberal Democrat seats by 7 and the number of Labour seats by 18. On the new boundaries, the Greens would not have won a seat in Brighton (but see the caveats below).” Labour would therefore suffer a net loss of seats relative to all other parties (in England) of 5. Although (by some measures) this is not quite as bad for Labour as the boundary changes in 2010, it is significantly worse than had been predicted by “independent” experts, who had predicted the Labour would be the largest loser but have a net gain compared with all other parties combined.
Looking at the effect for Labour by region, the worst outcomes are in London and the Midlands. The best outcome for Labour (although it won’t feel that way to individual Labour MPs since it is the English region with the biggest net loss of seats) is the North West.
In the last boundary changes which took effect in 2010, UK Polling’s estimate was that Labour’s net loss relative to other parties across Britain would be 28 seats (based on the 2005 result) or 8 seats with a 5% swing from Labour to the Tories which is what happened (see note below). As set out in the table below, their estimate of the effect on Labour of these proposed boundary changes is lower (using the previous prediction produced by Lewis Baston for Scotland and Wales).
The estimated effect, by region, of the proposed boundary changes by political party
Con Lab Lib Dem Others Seats Labour rel to other parties
East -1 -1 0 0 -2 0
South West 0 0 -2 0 -2 +2
South East 1 0 -1 -1 -1 +1
London 1 -5 -1 0 -5 -5
East Mids 0 -2 0 0 -2 -2
West Mids -1 -4 0 0 -5 -3
North West -3 -2 -2 0 -7 +3
North East -1 -1 -1 0 -3 +1
Yorks -1 -3 0 0 -4 -2
ENGLAND -5 -18 -7 -1 -31 -5
WALES -4 -5 -1 -10 0
SCOTLAND 0 -4 -3 0 -7 -1
N IRELAND 0 0 0 -2 -2 +2
UNITED KINGDOM -9 -27 -10 -4
Lewis Baston, Senior Research Fellow at Democratic Audit and former director of research at the Electoral Reform Society, produced a detailed prediction of the effect of the proposed Boundary changes. It had suggested that the Tories would lose 15 seats, Labour 18, the Lib Dems 14 and others 3. That is equivalent to a gain for Labour relative to all other parties of 16. Using his estimate for Scotland and Wales and the UK Polling estimate for England will bring the British total change for Labour relative to all other parties to +6 (or +4 including Norther Ireland).
Estimates (they are never predictions) of the effect of boundary changes is normally based on how the actual result of the last election on the old boundaries would have been counted based on the new boundaries. Votes in the old constituencies are allocated between the new constituencies using local election results as a guide. This doesn’t amount to a prediction of the effect of the boundary changes since many people vote tactically, based on the nature f their constituency — so if you change the boundaries, they may change their tactical voting.
Furthermore, an estimate is therefore based on the state of the parties at that (the last) election, without taking account of any change in the national state of the parties. It is possible to produce estimates for the effect of different uniform swings as UK Polling did here, but there are, of course, subject to greater error and many more caveats.