Boris Johnson was embroiled in a diplomatic row with Brussels on Friday night after he was accused of using a four-letter word to dismiss an ambassador’s question about the post-Brexit needs of British business.

EU diplomats have claimed that during a Foreign Office reception to celebrate the Queen’s birthday last week, the Foreign Secretary was asked about the fears of some business leaders over Brexit and replied: “f*** business.”

He was also overheard talking about Theresa May’s moves towards a softer Brexit and saying: “We will fight it and we will win.”

Mr Johnson was in conversation with Belgium’s ambassador to the EU Rudolf Huygelen at the event in Lancaster House, London, when he was overheard by two diplomatic sources making the comments.

Mr Johnson, the UK’s chief diplomat, admitted that Britain was more divided now than it had been since the English Civil War, after a speech in which he rhapsodised over the “wonderful project called Brexit”, it is claimed.