British Prime Minister Rishi Sunak says he has accepted minister Gavin Williamson’s resignation “with great sadness” and was grateful for his personal support and loyalty.

Mr Williamson said on Tuesday (local time) he was quitting to “comply fully” with an investigation into whether he had bullied colleagues while in previous roles.

“I support your decision to step back and understand why you have taken it … I would like to thank you for your personal support and loyalty,” Mr Sunak said in a letter to Mr Williamson published by the government.

Mr Sunak has been under pressure for the choice of some of his ministers after he was elected as Britain’s third prime minister in two months.

He appointed Mr Williamson, who had previously been fired as defence minister and education minister by Mr Sunak’s predecessors, to a ministerial role in the cabinet office two weeks ago.

However, the Sunday Times and other British newspapers have since reported that Mr Williamson had treated government officials aggressively and sent expletive-laden messages to colleagues.

Mr Williamson said in a letter to Mr Sunak on Tuesday he was complying with a complaints process and while he rejected the characterisation of the messages, he recognised they were becoming a distraction for the government.

“I have therefore decided to step back from government so that I can comply fully with the complaints process that is under way and clear my name of any wrongdoing,” he said in the letter, which he published on Twitter.

“It is with real sadness that I tender my resignation.”