Vaughan Gething, the first minister of Wales, announced his resignation on Tuesday after less than four months, amid a controversy over campaign donations that prompted a vote of no confidence in his leadership.

Mr. Gething, a Labour Party politician who became the first Black person to lead a national government in Europe when he was elected the head of the Welsh Parliament in March, denied any wrongdoing as he announced in a written statement that he was stepping down.

“A growing assertion that some kind of wrongdoing has taken place has been pernicious, politically motivated and patently untrue,” said Mr. Gething, as he delivered the same statement later in front of the Welsh Parliament, known as the Senedd, adding that in his 11 years as a lawmaker, he had “never ever made a decision for personal gain.”

Wales, like Scotland and Northern Ireland, is part of the United Kingdom but also has its own devolved government, which makes local laws and enacts national legislation and policies. Mr. Gething became the first minister after the resignation of a long-serving predecessor, Mark Drakeford, winning a tight leadership election within Wales’s governing Labour Party.

But he lost a confidence vote in the Welsh Parliament last month over his acceptance of campaign donations from a company whose owner had twice been convicted of environmental offenses.

That company, Dauson Environmental Group, donated a total of £200,000, or about $259,000, to Mr. Gething’s leadership campaign in two separate payments, one in December last year and another in January. David Neal, the company’s director, was convicted in 2013 after another of his companies, Atlantic Recycling, was found to have illegally dumped waste in protected wetlands. In 2017 he was convicted again for not removing that waste. The company pleaded guilty in court to another offense in January 2024.