Mr. Darroch described the Trump administration in the leaked emails as “clumsy and inept.” Mr. Trump responded by describing the ambassador as a “very stupid guy,” adding that the White House would no longer deal with him.

The bickering cast a shadow over the relationship between London and Washington at a crucial time when Britain was hoping to cultivate closer economic ties with the U.S. after Brexit.

Diplomatic corps: The reaction among other ambassadors in Washington to Mr. Darroch’s emails has been uniform. “It could have been any of us,” said a serving ambassador, who spoke on the condition of anonymity.

The winners of Trump’s trade wars?

American steel, aluminum, lumber, solar and washing-machine businesses have long complained about foreign competition — often from China — and sought tariffs.