FILE PHOTO - Britain's Prime Minister Theresa May delivers a speech at headquarters of Joint Forces Command in Northwood, London, Britain July 8, 2019. Matt Dunham/Pool via REUTERS

LONDON (Reuters) - Prime Minister Theresa May said she regretted that Britain’s ambassador to the United States had felt the need to resign, adding that officials needed to be able to give “full and frank advice”.

Kim Darroch resigned on Wednesday after Donald Trump labelled him “stupid” and “wacky” following the release of confidential memos from the envoy in which he branded the U.S. president’s administration inept.

“This morning I have spoken to Sir Kim Darroch. I have told him that it is a matter of great regret that he has felt it necessary to leave his position,” May told parliament.