UK By-Elections 2024-2026
Every Westminster by-election since the July 2024 General Election - full results, swings and what they signal for 2029.
Why by-elections matter
By-elections occur when a sitting MP dies, resigns or is disqualified. Contested mid-Parliament, they consistently produce larger swings than general elections - voters feel less pressure to vote tactically and often use the contest to send a message to the government. The 2024-2026 by-election cycle has become a live laboratory for Reform UK's electoral viability, with the party converting strong polling into actual seats for the first time.
Full Results: All By-Elections 2024-2026
| Constituency | Date | Result | Lab % | Con % | Reform % | Green % | Key story |
|---|---|---|---|---|---|---|---|
| Kingswood | Feb 2024 | Lab hold | 35% | 27% | 14% | 7% | Labour held narrowly; Reform entered double figures in a solid Conservative seat |
| Wellingborough | Feb 2024 | Lab gain from Con | 47% | 24% | 13% | 4% | Massive Labour gain; Reform already emerging as major third force |
| Blackpool South | May 2024 | Lab hold | 48% | 17% | 17% | 5% | Reform matched Conservatives in a seaside town hit by coastal decline |
| Runcorn & Helsby | May 2025 | Reform gain | 33% | 11% | 38% | 5% | Historic: Reform UK first by-election win. Swing of 25+ points from Labour |
| Wigan | Oct 2025 | Lab hold (narrow) | 36% | 10% | 34% | 7% | Labour survived by just 3 points; Red Wall seat now genuinely marginal |
| Blyth & Ashington | Jan 2026 | Reform gain | 32% | 9% | 41% | 6% | Labour heartland held since 1935 falls; 24+ point swing to Reform |
| Newark | Mar 2026 | Con hold vs Reform | 18% | 35% | 32% | 6% | Conservatives held off Reform; Labour collapsed to third |
Reform UK Vote Share: By-Election Trajectory
What the By-Elections Tell Us About 2029
Reform UK wins at Runcorn (May 2025) and Blyth & Ashington (Jan 2026) confirmed the party can convert polling leads into Westminster seats. Both wins came in formerly safe Labour territory, demonstrating that the Red Wall - already cracked by the Conservatives in 2019 - is now fragmenting along a new Reform axis.
Labour's majority in Wigan was reduced to under 3 points in October 2025. Blyth & Ashington - which returned a Labour MP continuously since 1935 - is the starkest indicator yet. If these trends persist to 2029, Labour could lose 40-70 northern and Midlands seats currently considered part of its core base.
The Conservatives polled just 9% in Blyth & Ashington - their lowest ever in the constituency. Even Newark, a traditionally safe blue seat, saw Reform close to within three points. The ability to hold existing 121 seats at the 2029 General Election is now in serious question, particularly in northern marginals.
Despite polling at 35-41% in several by-elections, Reform UK's national vote share is concentrated unevenly across constituencies. Under First Past the Post, geographic efficiency of votes determines seat count. Reform's path to government still requires concentrating votes in winnable seats rather than running up majorities everywhere.
The 2029 projection from by-election data
Applying by-election swing patterns uniformly to a general election is dangerous - turnout is far higher in general elections and some voters return to their preferred party when stakes are national. However, if Reform UK's by-election vote shares (averaging 27% across all seven contests) were replicated nationally at 28-30% in 2029, models suggest the party could win 100-160 seats under FPTP - enough to deny Labour a majority and potentially form the official opposition. Labour's parliamentary majority is currently so large (410 seats) that even a 15-point national swing to Reform would leave them with a working majority, but the composition of Parliament would look radically different.
Featured By-Election Deep-Dives
Runcorn & Helsby
Reform UK's first ever Westminster by-election win. A 25+ point swing from Labour. The moment the political map changed.
Blyth & Ashington
The ultimate Red Wall fortress falls. Labour held this seat continuously since 1935. Reform's 41% makes it the most dramatic result since 2024.
How has Reform UK performed in UK by-elections since 2024?
Reform UK has dramatically increased its vote share in every Westminster by-election since the July 2024 General Election. Starting at 13–17% in the three February–May 2024 contests, the party reached 38% at Runcorn & Helsby (May 2025) and 41% at Blyth & Ashington (January 2026). Reform has now won two Westminster by-elections outright — both in formerly safe Labour northern England seats — confirming the party can convert its national polling lead into actual seats. The average Reform UK vote share across all seven by-elections since 2024 is approximately 27%.
What do by-election results tell us about future general elections?
By-elections are imperfect but useful mid-term signals. Turnout is lower (typically 35–50% versus 60%+ at general elections), protest voting is amplified, and parties concentrate resources on single seats. However, the 2025–2026 by-elections show consistent patterns: Labour consistently polls 10–15 points below its 2024 general election share in English seats; Reform UK consistently outperforms its 2024 result; and the Conservatives have collapsed to single figures in northern England. If these mid-term patterns hold to 2029, the composition of Parliament would change radically even if Labour retains its majority.
Which seats have changed hands in UK by-elections since 2024?
Two seats have changed hands since the July 2024 General Election: Runcorn & Helsby (May 2025) fell from Labour to Reform UK by just 6 votes after a recount — the closest by-election result in decades — and Blyth & Ashington (January 2026) fell to Reform UK on a 24+ point swing. Labour had held Blyth & Ashington continuously since 1935. Three other contests (Wigan, Kingswood, Wellingborough) were Labour holds but with dramatically reduced majorities. Only Newark held for the Conservatives against a strong Reform challenge. Full Runcorn result →
Could Reform UK win enough seats to form a government in 2029?
Forming a government would require winning roughly 326 seats. By-election projections applied uniformly suggest Reform UK could win 100–160 seats at a 2029 general election if current polling holds — enough to be the largest opposition party and potentially deny Labour a majority, but short of government. The key obstacle is FPTP’s geographic efficiency problem: Reform’s vote share is currently spread broadly rather than concentrated in the right seats. Reform would need to target specific marginals rather than running up large majorities in safe Labour northern seats it already wins comfortably. 2029 election forecasts →
What is typical turnout at UK by-elections and why does it matter?
UK by-elections typically see 30–45% turnout versus 60–70% at general elections. Runcorn & Helsby (May 2025) recorded 36.7% turnout compared to 62.4% at GE2024; Blyth & Ashington (Jan 2026) saw 34.1% versus 60.1%. Low turnout systematically benefits Reform UK because their highly motivated base votes at disproportionately high rates while casual Labour voters stay home. In absolute vote terms, Reform UK’s totals barely changed between 2024 and the by-elections — Labour’s absolute vote count halved. At a 2029 general election, higher turnout would narrow the gaps, but seats with 14,000+ majorities still fell.
What do the 2025-2026 by-elections tell us about Labour’s 2029 defence map?
The by-elections transformed Labour’s 2029 risk assessment. Before Runcorn, seats with 14,000+ majorities were considered impregnable. After two consecutive losses of such seats, the party’s strategists now treat any northern England or Midlands seat with a GE2024 majority below 10,000 as genuinely competitive. Labour responded with policy adjustments on immigration and welfare, but polling shows these changes have not yet reversed the mid-term trajectory. The Starmer government’s -44% net approval in May 2026 — the worst for a PM at this stage since records began — indicates the by-election pattern is driven by deep-seated dissatisfaction, not just a protest bounce. 2029 battleground seats →
Explore More
Runcorn & Helsby 2025
Reform UK’s first Westminster by-election win. Full results, swing analysis and what it means for Labour’s Red Wall.
Blyth & Ashington 2026
Labour held since 1935. Reform UK’s 41% and a 24-point swing make it the most dramatic result of the current Parliament.
2029 General Election
What do current by-election and national polling trends mean for the 2029 General Election? Seat projections and party trajectories.
Reform UK
Full Reform UK polling tracker — national polls at 28%, two Westminster seats, and the Farage strategy heading to 2029.
Voting Intention Tracker
GB-wide poll of polls updated weekly. See how by-election results compare to the national picture.
How FPTP Works
Why Reform UK can win 28% nationally but struggle to win seats proportional to its vote — the mechanics of First Past the Post explained.
Sources & Further Reading
By-election results are published by the House of Commons Library. For in-depth analysis of how by-elections signal broader trends, see our by-elections explainer and the current voting intention tracker.