The US president's renewed attack on the prime minister and Sir Kim Darroch came after leaked memos revealed the ambassador branded the Trump White House "inept" and "dysfunctional".
"The wacky Ambassador that the U.K. foisted upon the United States is not someone we are thrilled with, a very stupid guy," Mr Trump tweeted on Tuesday morning. "He should speak to his country, and Prime Minister May, about their failed Brexit negotiation, and not be upset with my criticism of how badly it was handled."
Mr Trump on Monday announced the US would "no longer deal" with Sir Kim who was "not liked or well thought of" within the country. He also criticised Ms May for the "mess" he claimed she had created over Brexit.
The escalating diplomatic crisis between the US and Britain was sparked when the Mail on Sunday obtained diplomatic memos from Sir Kim, who in them described the US administration as "uniquely dysfunctional” and questioned whether it “will ever look competent”.
There is no suggestion he was upset over Mr Trump's criticism of the UK's negotiation strategy with the European Union over Brexit.
In one scathing assessment, Sir Kim wrote: “We don’t really believe this administration is going to become substantially more normal; less dysfunctional; less unpredictable; less faction riven; less diplomatically clumsy and inept.”
The top diplomat also suggested that in order to communicate with the US president “you need to make your points simple, even blunt”.
The Foreign Office, which on Sunday launched an investigation into the source of the leak, has been contacted for comment.
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