If 4.25% of the electorate switch from Labour to a party with better climate policy, particularly one that could win in their seat, the next general election result would look something like this:

Labour: majority of 0 seats
Conservative: 121 seats short of a majority

Methodology:

Start from VoteClimate's Forecast For The Next General Election where the vote shares (GB) are Labour: 44% | Conservative: 27% | Liberal Democrat: 11.3% | Green: 6.8% | Reform: 6.1%.
Subtract 4.25% of the electorate from Labour's votes in each seat.
Add 4.25% of the electorate to the party with the best climate policy that can win or, if none can win, to the party with the best climate policy.
For this example, we've estimated that the parties rank on climate policy best to worst as follows:
Green, Plaid Cymru, Liberal Democrat, SNP
NB: yes, it's highly simplistic to imagine the switch will be only away from Labour, but useful to estimate the size of the swing required.

[Last updated: June 2026]

If people switch votes as per above, the seats would transfer between parties as follows:

Number of Seats	Switch from Party	To Party
48	Labour	Conservative
17	Labour	SNP
15	Conservative	Liberal Democrat
3	Labour	Plaid Cymru
1	Labour	Liberal Democrat
1	SNP	Liberal Democrat

What If 4.25% Of The Electorate Switch From Labour To A Party With Better Climate Policy?