Reform UK Wales leader resigns after arrest on suspicion of assault

The leader of Reform UK in Wales, Dan Thomas, has resigned after being arrested on suspicion of assault and coercive behaviour.

His sudden departure on Tuesday came alongside another major blow for the party, as Sarah Cooper-Lesadd, one of its Members of the Senedd (MSs), defected to Plaid Cymru.

What happened to Dan Thomas?

On Sunday 13 September, Gwent Police arrested a 45-year-old man from the Aberbargoed area on suspicion of assault and engaging in controlling or coercive behaviour. Officers later released him on bail pending further enquiries.

Following the arrest, Mr Thomas announced his resignation as leader of Reform UK in Wales. In a statement, he said he was standing down for "personal reasons" but maintained his innocence, saying he had "done nothing wrong" and had been "released without charge."

Mr Thomas added that he did not want the coming headlines to distract from the work of his Senedd colleagues. He intends to continue serving his constituents as the MS for Casnewydd Islwyn.

Why did Sarah Cooper-Lesadd defect?

At almost the exact same time as Mr Thomas's resignation, Ms Cooper-Lesadd announced she was leaving the party to join Plaid Cymru, the left-leaning Welsh nationalists who lead the Welsh government.

In a scathing statement, Ms Cooper-Lesadd accused Reform of lacking a serious approach to politics. "They are far more interested in division, opposition and headlines than in finding solutions," she said, adding that the party is "not serious about governing Wales."

Plaid Cymru's Senedd group chair, Marc Jones, welcomed her decision, saying it showed Reform was "descending into chaos."

Who is Dan Thomas and how did he lead Reform?

Mr Thomas grew up in south Wales but spent much of his adult life in London, where he served as a Conservative councillor and led Barnet council from 2019 to 2022. He defected to Reform in June 2025 and moved back to Wales later that year.

In February, Nigel Farage appointed him to lead the Welsh branch of Reform. The appointment of an outsider was widely seen as an attempt to distance the party from its former Welsh leader, Nathan Gill, who was jailed for accepting bribes to promote Russian interests in the European Parliament.

Under Mr Thomas's leadership, Reform made historic gains in May's elections to the newly expanded 96-seat Senedd. The party surged from having just two politicians in Cardiff Bay to 34, making it the official opposition.

What is the political reaction?

The double blow has prompted fierce criticism from political rivals.

Ken Skates, the leader of the Welsh Labour group, said the crisis raised serious questions about Nigel Farage's judgement, pointing to a series of scandals including the jailing of Mr Gill.

Conservative leader Kemi Badenoch said there was "a pattern" of problematic former Tories defecting to Reform. "He took a large number of very problematic people from the Conservatives," she wrote on social media. "Reform is where they belong."

What happens next for Reform in Wales?

Reform politicians in the Senedd must now choose a new leader.

Llyr Powell, a Reform MS, said the group would soon begin a formal selection process, with a new leader expected to be chosen by the end of September.

Mr Powell added that Mr Thomas was "panicking" at the prospect of his private life being thrust into the public eye. "We need to all remember there are human beings at the end of this," he said.