Sir Kim Darroch has resigned as UK ambassador to the US as a row over leaked emails critical of President Trump’s administration escalates.

Theresa May said Sir Kim’s departure was a matter of deep regret after the ambassador said it was impossible for him to continue.

Tory leadership candidate Boris Johnson has faced strong criticism for failing to fully support him.

President Trump said on Monday that the US would not deal with Sir Kim.

The US President had branded him a very stupid guy after confidential emails emerged where the ambassador had called his administration clumsy and inept.