Dan Thomas has resigned as leader of Reform UK in the Welsh Senedd, days after being arrested on suspicion of assault and coercive and controlling behaviour. He was absent from First Minister's Questions on the day of his resignation, with his party initially citing "personal reasons" before he confirmed in a statement that he had been reported to police, arrested and released without charge. The resignation is a fresh setback for Nigel Farage's party, which is also facing scrutiny over recent record-breaking donations and, on the same day, lost an AM to Plaid Cymru.

Gwent Police confirmed a 45-year-old man from the Aberbargoed area was arrested on Sunday 13 September on suspicion of assault and controlling or coercive behaviour, and has been bailed pending further inquiries. Thomas, a former Conservative leader of Barnet Council who defected to Reform in summer 2025, said he had done nothing wrong but did not want the story to distract from his party's work, and pledged to continue as an MS for Newport and Islwyn. He had led Reform to become the largest opposition group in Welsh political history with 34 seats, though the party fell short of taking control of the Senedd, which went to Plaid Cymru's Rhun ap Iorwerth. His predecessor as Welsh Reform leader, Nathan Gill, was jailed last year for accepting bribes to make pro-Russian speeches.