Reform UK's leader in Wales, Dan Thomas, has resigned from his position following his arrest on suspicion of assault and controlling or coercive behaviour. Thomas, a Member of the Senedd for Casnewydd Islwyn, was arrested on Sunday, September 13th, and subsequently bailed pending further enquiries by Gwent Police.

Thomas, who was appointed Welsh party leader by Nigel Farage in February, stated in a party release that he was stepping down for personal reasons. He maintained that he had been released without charge and had done nothing wrong. The resignation comes just months after the party's significant success in the May Senedd elections, where Reform UK grew from two to 34 elected members, becoming the largest opposition group in the Welsh Parliament.

In his statement, Thomas expressed his honour in leading Reform Wales and witnessing its growth. "With deep regret, I am now standing down from this position due to personal reasons," he said. He added that he would continue to serve his constituents and support the party's next leader.

The arrest and subsequent resignation have drawn sharp criticism from other political parties in Wales. Plaid Cymru, the party forming the Welsh government, described the situation as "Reform UK descending into chaos." The party's Senedd group chair, Marc Jones, also pointed to the recent defection of Reform MS Sarah Cooper-Lesadd to Plaid Cymru as evidence of Reform UK's focus on division rather than governance.

Welsh Labour leader Ken Skates commented that the news was "incredible" and that many questions would need answering. He suggested that Thomas's appointment by Nigel Farage demonstrated "appalling judgement" on the part of the Reform UK leader. The Conservative Shadow Secretary of State for Wales, Mims Davies, raised concerns about Reform UK's judgment and leadership at all levels, referencing recent controversies.

Welsh Liberal Democrat Leader Jane Dodds also weighed in, stating that "the wheels are rapidly coming off Reform in Wales and the entire country." Thomas, who grew up in Blackwood, was first elected to the Senedd in May and had become the leader of the opposition.

Gwent Police confirmed that a 45-year-old man from Aberbargoed, Caerphilly, was arrested on suspicion of assault and engaging in controlling/coercive behaviour. He was bailed pending further enquiries. Thomas did not participate in First Minister's Questions on the day the news broke.

The departure of Thomas is the latest in a series of challenges for the Reform UK party in Wales. This development, coupled with the defection of Sarah Cooper-Lesadd, raises questions about the party's stability and future direction in the region.