Keir Starmer’s Labour suffers seismic byelection defeat to Plaid Cymru in Wales

Loss of Welsh assembly seat in stronghold deals blow to prime minister’s leadership

Plaid Cymru's Lindsay Whittle celebrates after being declared winner for the Caerphilly Senedd byelection. Photograph: Andrew Matthews/PA Wire
Plaid Cymru's Lindsay Whittle celebrates after being declared winner for the Caerphilly Senedd byelection. Photograph: Andrew Matthews/PA Wire

Keir Starmer’s Labour Party has suffered a local byelection defeat in a traditional Welsh stronghold, losing Caerphilly for the first time in any election in a century to the nationalist party Plaid Cymru.

The 3,848-vote majority secured by Plaid Cymru’s Lindsay Whittle in the Welsh Senedd assembly seat deals a blow to Starmer’s leadership and comes in advance of broader elections in Wales in May.

“We want a better deal for every corner of Wales,” Whittle said in his victory speech on Friday. “The big parties need to sit up and take notice. Wales, we are at the dawn of new leadership; we are at the dawn of a new beginning.”

Whittle, who had failed on 13 previous occasions to become either MP or Senedd member for Caerphilly, described Labour as a “dying beast” that was on its way out after 100 years of power in Wales.

The result highlights how Labour is exposed on its left flank after tacking to the right on issues including immigration and crime in an attempt to counter the rise of Reform UK.

Labour's stunning byelection loss in Wales shows parties who cannot adapt will be crushedOpens in new window ]

Labour’s popularity in Wales has also nosedived since former first minister Vaughan Gething stepped down last year after a scandal involving donations.

Eluned Morgan, the current Welsh First Minister, said: “Welsh Labour has heard the frustration on doorsteps in Caerphilly that the need to feel change in people’s lives has not been quick enough.”

However, Deputy First Minister Huw Irranca-Davies argued that Labour could still “bounce back” from the defeat. “I have to paraphrase Mark Twain: rumours about death are greatly exaggerated,” he said.

Reform UK leader Nigel Farage with his party's candidate Llyr Powell. Photograph: Ben Birchall/PA
Reform UK leader Nigel Farage with his party's candidate Llyr Powell. Photograph: Ben Birchall/PA

The failure of Nigel Farage’s party to seize the seat came as some relief to Labour, as Reform maintains a double-digit lead over Starmer’s party in national opinion polls.

Farage had visited the constituency three times during the campaign and a poll last week had suggested his party was ahead of Plaid by four percentage points.

Labour had represented the seat in the South Wales Valley for a century at Westminster and for more than 25 years – since devolution began – at the Senedd.

Friday’s result has no bearing on the party’s majority in Westminster, however. Chris Evans remains Labour MP for Caerphilly.

The assembly byelection result was declared at 2.10am on Friday. Whittle took 47 per cent, with 15,961 votes, beating Reform candidate Llŷr Powell into second place on 36 per cent, with 12,113 votes.

Reform’s Powell chose not to give a speech after failing to win the seat, which became vacant after the death of former Labour MS Hefin David in August.

But Zia Yusuf, Reform’s head of policy, said the party’s result was “remarkable”, saying: “This is a historic realignment in Welsh and British politics.”

The Labour candidate, Richard Tunnicliffe, picked up just 3,713 votes in its former stronghold, or 11 per cent, down from 13,289 in 2021.

The Tories’ Gareth Potter received just 690 votes, or 2 per cent.

The turnout of 50.43 per cent in the ballot was the highest in the history of byelections to the Welsh assembly.

Luke Tryl, director of polling group More in Common, said there appeared to have been significant tactical voting by left-wingers to block Reform, with minimal voting for either the Greens or Liberal Democrats.

“Voters in this race knew it was a Plaid-Reform contest and voted accordingly,” he said.

Rhun ap Iorwerth, leader of Plaid, said there had been an element of voters “wanting to stop Reform”.

Whittle becomes Plaid’s 13th member of the 60-strong Senedd in Cardiff Bay.

Reform UK had been the bookmakers’ favourite to win the contest after last week’s small opinion poll lead.

The defeat for Labour means the party has lost its effective majority in the Senedd, which it has previously sustained with the support of the assembly’s sole Liberal Democrat member.

Dropping from 29 to 28 seats in the 60-strong assembly now means Labour must turn to either Plaid or, possibly, one of the two independent members for support on Senedd votes.

The byelection result will be seen as a significant omen in advance of local and regional elections in May, across Wales, Scotland and England.

A defeat for Labour in the Senedd elections next spring could raise serious questions over Starmer’s leadership barely two years into his premiership.

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But the feeble showing for the Conservatives will also ring alarm bells for that party’s leader, Kemi Badenoch.

Reform’s Yusuf predicted: “The Senedd elections next May are now a battle between Reform and Plaid.”

- Copyright The Financial Times Limited 2025

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