FIRST Minister Nicola Sturgeon has hit out at Brexit Party leader Nigel Farage over his response to the resignation of UK ambassador to the United States Kim Darroch.

A leak of sensitive diplomatic messages had shown that Darroch believed Donald Trump’s administration to be “inept” – and he has now resigned, after Tory leadership contest frontrunner Boris Johnson failed to back him.

Responding to the news on Twitter, Farage wrote: "The right decision, time to put in a non-Remainer who wants a trade deal with America."

The First Minister replied to him to say that he was eyeing up the role for himself.

Sturgeon said: "Who could Farage be thinking of? The last thing that should happen is the politicisation of the civil service and the replacement of honourable diplomats with charlatans like this guy."

She had earlier harshly criticised the Tory government over its handling of the affair.

Darroch announced his resignation in a letter to Sir Simon McDonald, the permanent under secretary at the Foreign and Commonwealth Office.

In last night's Tory leadership debate, while Jeremy Hunt had said Darroch would remain in his post until he was due to resign at the end of the year, Johnson gave no commitment.

Instead, he said: “I have a very good relationship with the White House ... and it is very important we have a close friendship, a close relationship with the United States.”

Following Darroch's resignation, Sturgeon said: “It is shameful that Kim Darroch has effectively been forced out for doing the job that diplomats are appointed to do.

“Boris Johnson’s failure last night to stand up for him – and stand up to the behaviour of Donald Trump – spoke volumes.”

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In his resignation letter, Darroch wrote: "Since the leak of official documents from this embassy there has been a great deal of speculation surrounding my position and the duration of my remaining term as ambassador. I want to put an end to that speculation.

"The current situation is making it impossible for me to carry out my role as I would like.

"Although my posting is not due to end until the end of this year, I believe in the current circumstances the responsible course is to allow the appointment of a new ambassador.

"I am grateful to all those in the UK and the US, who have offered their support during this difficult few days. This has brought home to me the depth of friendship and close ties between our two countries. I have been deeply touched.

"I am also grateful to all those with whom I have worked over the last four decades, particularly my team here in the US. The professionalism and integrity of the British civil service is the envy of the world. I will leave it full of confidence that its values remain in safe hands."