Boris Johnson thought Sue Gray, the woman charged with investigating partygate, was a “psycho”, his former No10 director of communications has suggested.

Guto Harri added Mr Johnson came to the view that Ms Gray "lacked perspective" as her inquiry into Covid rule-breaking parties grew "completely out of all proportion".

Mr Harri also insisted Mr Johnson was not involved in a "fight" with King Charles over the monarch’s criticism of the Government’s Rwanda deportation scheme following reports he "squared up" to the then Prince of Wales at a Commonwealth summit.

But he said the former prime minister "rightly challenged" the King amid reports he had privately branded the plan to deport Channel migrants to Rwanda as "appalling".

When asked during an interview on LBC Radio how the former prime minister had described Ms Gray to him, Mr Harri said: "I don’t want to give away everything because I want people to go to Global Player this Thursday and download it [his new podcast].

“But if I were to say one word maybe that will be recurring in it, psycho Sue Gray would be part of it.

“And there was a sense that she lacked perspective as to what he had done… you will get the words.

'Showdown with King'

“But, you know, towards the end I think he rightfully thought that there was no perspective and things were completely out of all proportion in the way partygate was viewed.”

On Mr Johnson's apparent clash with King Charles,Mr Harri said "it wasn't a fight" but did describe it as a "bit of a showdown".

At the time, No 10 denied there had been a row, with Mr Johnson saying only that the two men had had a “good old chinwag.”

Last night, sources close to Mr Johnson said: “This account is simply inaccurate and does not reflect the conversation that took place. Boris Johnson has had nothing to do with this podcast, had no knowledge of it and deplores any attempt to report such conversations in public.”

Friends of Mr Johnson added that he deeply disapproved of the leaking of conversations with the heir to the throne and would never do so.

Writing in the Daily Mail, Mr Harri, a former BBC journalist, claimed the meeting between the then PM and future King at last year's Commonwealth Heads of Government summit was “less amicable” than it was painted at the time. '

“Boris briefed that the two had 'a good old chinwag' and had 'covered a lot of ground',” he said. What actually happened was less amicable.

“‘I went in quite hard', he told me at the time, essentially squaring up to the prince and confronting him about what he – as unelected royalty – had said about the actions of a democratically elected government.

"Prince Charles was busted. He had obviously expressed some criticism, and though he tried to play it down, Boris pointed out the obvious, [saying]: 'If you didn't say it we both know your people could ring the newspapers and kill the story. The fact they haven't done that says it all'."