By Friday night, Keir Starmer and much of the Westminster Labour group were quietly relieved that the local election results in England hadn’t been quite as bad as feared. In Wales, however, Labour’s collapse in the Senedd was even more total than the most pessimistic predictions.

For more than 100 years, Welsh Labour was the democratic world’s most successful election-winning machine, but the political behemoth limped into third place this week with just nine seats in a 96-seat parliament. A new chapter in Wales’s political and cultural history has opened: pro-independence Plaid Cymru is set to form a minority government.

“For those of us who’ve only known Labour domination … the fact that it could collapse with such dramatic completeness – it’s quite hard to convey the shock. It was just astonishing. Labour was absolutely mullered,” said Richard Wyn Jones, the director of the Wales Governance Centre at Cardiff University.

“We’ve known Labour was in deep trouble in the post-industrial valleys … but the fact that Plaid could win half of the 12 seats in Cardiff? Genuinely everywhere you look, it’s hard to identify any solid territory they can actually rebuild on.”

In an extraordinary admission of defeat before a single constituency result was declared, Labour released a statement saying it expected to return just 10 MSs out of 96 available seats in the newly expanded Senedd chamber. The party previously never held fewer than 26 seats in a 60-seat chamber.

The first minister, Labour’s Eluned Morgan, cut a tragic figure as the results were announced at the count in her west Wales constituency of Ceredigion Penfro. Three of the six seats available went to Plaid Cymru, two to Reform and one to the Conservatives, making Morgan the first ever leader of a government in the UK to lose their seat while in office.

She immediately resigned in a concession speech. The party announced on Saturday that Ken Skates, MS for Fflint Wrecsam and former cabinet secretary for transport, would serve as interim leader.

“I am proud of what Welsh Labour has achieved for this nation over so many years … But the people of Wales have rejected us and we owe it to the people of Wales to listen. To understand. And to rebuild,” she said.

Morgan received lengthy applause from the room. The successful candidates expressed admiration for the Cardiff-born first minister’s energetic campaign, and praised her career in public service.

But nothing Morgan could do would have been enough to stop the haemorrhage. Plaid Cymru’s messaging that a vote for the party was the only way to stop Nigel Farage’s Reform UK cut through, despite the introduction of a new, more proportional voting system.

And support for Labour was already ebbing before she took over in 2024 after the disastrous, short-lived tenure of her predecessor, Vaughan Gething.

Wales embarked on devolution more cautiously than Scotland and Northern Ireland, and initially very limited powers hampered Cardiff Bay administrations. Supporters insist the party held the line against 14 years of Conservative government in Westminster, protecting public services from the impact of austerity, Brexit and the Covid pandemic.

Welsh Labour partly had an incumbency issue – but it also had to contend with the growing criticism of its track record in office, much of it justified. After nearly 30 years of Labour management of public services, Wales has fallen behind the other UK nations, particularly in poverty, education and the NHS, which is underperforming despite significant spending increases.

Starmer’s election was expected to strengthen Welsh Labour as a “partnership in power” in Cardiff and London, but his unpopularity dragged it down instead – and left the Cardiff Bay administration unable to blame the Conservatives for perceived failings.

Starmer did not appear to have much interest in how the Welsh wing of the party fared, warning his cabinet against “overly deferential relations” with the devolved governments.

Last year, 11 Labour Senedd members took the extraordinary step of writing to the prime minister claiming his administration had been either “deeply insensitive” to Wales or guilty of “constitutional outrage” by failing to deliver on devolution promises, including justice, policing and the crown estate.

Alun Davies, a long-serving Labour member of the Senedd who lost his seat in Blaenau Gwent, told Channel 4 News that the party’s defeat was “manufactured in Downing Street” by Starmer’s “disregard” for Wales.

“This is not simply midterm blues or a protest vote. This is a very deep turning away from a party that people have felt almost a cultural attachment to for more than a century,” he said.

Another Labour source said: “This result has been a long time coming. On the doors, people felt let down by the Welsh government’s handling of the NHS and education. We have to take responsibility for that. People also haven’t felt the changes of a UK Labour government fast enough. It’s on all of us to rebuild the party in Wales.”

Welsh Labour will elect a new leader in the coming weeks, but the contest will reflect the scale of its defeat. There are only nine people to choose from, since the leader must be a Senedd member – and nominees need the backing of 20% of MSs.

The party must be “more muscular about its Welshness” if it wants to survive, said Laura McAllister, a professor of public policy at Cardiff University.

“There’s a steady increase in the number of people who see themselves as Welsh only, or Welsh first and British second. If [Labour] want to capture that group, they need to show again that they are different to UK Labour, with their own identity and agenda, as in the early days of devolution and the ‘clear red water’,” she added.