Dan Thomas, who was elected as leader of the opposition in Wales's May parliamentary elections, has resigned from his position as Reform UK's Welsh leader following his arrest on suspicion of assault and controlling or coercive behaviour. The former Conservative councillor, appointed to lead the party in Wales by Nigel Farage in February, announced his decision on Tuesday 17 September afternoon, stating he did not wish to become a distraction from his party's work in the Senedd. Reform's chief whip Llŷr Powell subsequently confirmed that the party's membership will not have a vote on Thomas's replacement, despite the party's constitution allowing a membership ballot if multiple candidates emerge.
Thomas was arrested on Sunday 15 September and released on bail pending further inquiries. Gwent Police confirmed that a 45-year-old man from the Aberbargoed area was taken into custody on suspicion of assault and engaging in controlling or coercive behaviour. In his statement, Thomas maintained his innocence, saying:
Over the weekend, I was reported to the police and was released without charge. I stress that I have done nothing wrong, but I do not want the coming headlines to be a distraction from the fantastic work our Senedd team is doing in holding this government to account.
According to reporting on the resignation, Thomas indicated he would remain as a Senedd member despite stepping down from the leadership role. His decision to resign came on the same day that Reform MS Sarah Cooper-Lesadd announced her defection to Plaid Cymru, marking a significant setback for a party that had invested heavily in establishing itself as a major force in Welsh politics.
How did Reform UK achieve such prominence in Wales?
Reform UK's emergence as the second-largest party in the Welsh parliament represented an unprecedented breakthrough for the party in Wales. In May's election, Reform secured 34 seats in the newly expanded 96-seat Senedd, finishing behind only Plaid Cymru's 43 seats. The party increased its vote share dramatically from 1% in 2021 to 29% in 2026, outperforming any previous Welsh Conservative result on record. According to additional reporting on the party's performance, Thomas had described Reform as having progressed from "zero to 34 elected members" and characterised it as "the largest opposition group in Welsh history."
Farage's selection of Thomas as Welsh leader was intended to signal a fresh start for the party in Wales. Thomas, a former leader of Barnet council in north London between 2019 and 2022, had defected to Reform from the Conservative Party in summer 2025. He stood down as a councillor in December to relocate to his hometown in the south Wales valleys. The appointment was designed to distance Reform from its previous Welsh leader, Nathan Gill, who was imprisoned for accepting bribes in exchange for making pro-Russia statements while serving as a Member of the European Parliament.
What tensions had emerged within Reform's Welsh group?
Despite Reform's electoral success, the party's performance in the Senedd since May has been marked by internal difficulties and unparliamentary conduct. Frequent reports of infighting within the Reform group have surfaced, and the perception that Thomas was parachuted in by party headquarters rather than emerging organically from the Welsh membership created friction. According to reporting from a national broadcaster, Reform had already opened an investigation into a separate incident involving one of its audience members, indicating the party was grappling with wider internal fallout beyond Thomas's situation.
Thomas notably remained silent on Monday 16 September when nationalist first ministers from Wales, Scotland and Northern Ireland declared that "Westminster's time is coming to an end," a statement that might have been expected to prompt comment from the leader of Wales's largest opposition group. His absence from the first plenary session of the new Senedd term and questions for the first minister on Tuesday afternoon was initially attributed to "personal reasons" by Reform.
Why did Sarah Cooper-Lesadd defect to Plaid Cymru?
At almost the same moment Thomas announced his resignation, Reform MS Sarah Cooper-Lesadd revealed she was switching to Plaid Cymru, a party positioned at nearly the opposite end of the political spectrum. Her defection represented a direct rejection of Reform's approach and priorities. Cooper-Lesadd stated:
[Reform UK] … are not serious about governing Wales. They are far more interested in division, opposition and headlines than in finding solutions. Their Senedd group is a staging post in the effort to get Nigel Farage into Downing Street and that was glaringly obvious at its conference this week.
The defection underscored growing frustration within Reform's ranks about the party's direction and its focus on national rather than Welsh politics. Cooper-Lesadd's characterisation of the Senedd group as a stepping stone for Farage's ambitions to reach Downing Street suggested that some elected members felt the party was not genuinely committed to Welsh governance.
How have political opponents responded?
Ken Skates, leader of the Labour Senedd group, seized on the turmoil to criticise Farage's track record of leadership appointments in Wales. Skates said:
Nigel Farage chose to make Nathan Gill his leader in Wales and he turned out to be a Russian asset. He chose to take £5m from a crypto billionaire that triggered an investigation. He chose to meet two men in a pub in Clacton to discuss breaching electoral law. And he chose to make Dan Thomas his leader in Wales, who has now quit suddenly. That Farage and Reform are in such a dire mess is bad enough, but it's also bad for Plaid, welcoming a Reform defector who just a few weeks ago characterised herself as being rightwing.
Skates's comments highlighted a pattern of difficulties surrounding Farage's leadership decisions and the party's broader governance challenges, while also questioning the wisdom of Plaid Cymru's decision to accept Cooper-Lesadd as a member.
How will Reform select a new Welsh leader?
Reform's membership will not have a vote on Thomas's successor, according to the party's chief whip Llŷr Powell. Speaking to Radio Wales Breakfast on Wednesday 18 September, Powell stated that Reform's 33 Senedd members will have a vote only if more than one candidate comes forward. He said:
So there's no difference there, but we've got a constitution. We're following it through. Nominations can open and this process, I'm convinced, will be done by the end of the month so we can once again focus on what is the priority, which is the people of Wales and holding this government to account.
Powell defended the decision by noting that none of the other group leaders in the Senedd had been elected by their members. He declined to confirm whether he was happy for Thomas to remain a Reform Senedd member during the police investigation, and refused to rule out being a contender himself, saying he had "not even considered anything like that."
Several potential candidates have already ruled themselves out of the contest. James Evans, a Reform MS who had been thought to be in the running, announced on Wednesday that he would not put his name forward. In a statement, Evans said:
As most of you know I always put my family first. After having consulted with my family and my wife, I decided on this occasion I will not be putting my name forward for the leadership and running in the contest that will come. I hope that the party can unite behind a single candidate, and we can get on with the job of representing the people here in Wales and opposition and fighting for those communities who feel left behind. I had majority of support in the group, but I do not think a competition at this time will be beneficial for anybody.
Powell and interim leader Helen Jenner are thought to be among the potential candidates to replace Thomas, although neither had made their interest public by Wednesday afternoon. Cai Parry-Jones and Jason O'Connell are believed to have ruled themselves out. Reform party members met in Cardiff Bay on Wednesday morning to discuss their next steps, with a party official from London attending to oversee proceedings. Thomas was understood to have been present in person for the meeting.
What happens next?
Gwent Police has confirmed that Thomas remains on bail pending further inquiries into the assault and controlling or coercive behaviour allegations. No court date has been scheduled, and the police investigation represents the next significant development in the case. Reform has not announced any of its own disciplinary action against Thomas.
Reform UK now faces the challenge of selecting a new Welsh leader and attempting to stabilise its group in the Senedd following the twin blows of Thomas's resignation and Cooper-Lesadd's defection. Powell indicated the party aims to complete the leadership selection process by the end of September. The party's ambitious plans to expand its influence in traditional Labour strongholds across Wales have been significantly complicated by these developments.
Key Facts
- Dan Thomas was arrested on Sunday 15 September on suspicion of assault and controlling or coercive behaviour, and was released on bail pending further inquiries
- Reform UK won 34 seats in May's Welsh parliament election, increasing its vote share from 1% in 2021 to 29% in 2026
- Thomas's appointment as Welsh leader in February was intended to distance Reform from its previous leader Nathan Gill, who was jailed for accepting bribes related to pro-Russia statements
- Sarah Cooper-Lesadd defected from Reform to Plaid Cymru on the same day Thomas resigned, citing the party's lack of seriousness about Welsh governance
- Reform's membership will not vote on Thomas's successor; the party's 33 Senedd members will only have a vote if multiple candidates emerge
