The former head of Britain’s diplomatic service said Boris Johnson was the worst prime minister he worked under during his almost 40 year-stint in government.
Sir Simon McDonald – who served under seven Tory and Labour prime ministers – said Mr Johnson was a “charismatic” but “chaotic” leader.
“[Margaret] Thatcher was the best and Johnson was the worst,” Lord McDonald told Sky News in a revealing interview.
Sir Simon, who started as a diplomat in 1982 and became permanent under-secretary at the Foreign Office until 2020, said all seven PMs he served under were “good at some things and weak at others”.
Ms Thatcher was “very difficult, prickly character for the system”, said the Lord McDonald – but said her clarity and sense of purpose made her “one of our most effective prime ministers in 300 years”.
The Whitehall mandarin said John Major was “one of the most methodical men I’ve ever seen” and praised Tony Blair for being “the best” communicator he had seen over his four decades.
However, the ex-Foreign Office chief appeared criticised the Labour PM over the invasion of Iraq. “In retrospect some of his biggest policy calls were just wrong, but at the time the domestic policy, the Ireland policy was right.”
Labour PM Gordon Brown was “the best at finance” but was not good at communicating, he added. “He wore his anxieties on his face. To look as if you’re burdened makes your task more difficult.”
Sir Simon said David Cameron was “in some ways the easiest to work for”, and described fellow Tory PM Theresa May as a “very methodical person” who was “hobbled” by Brexit.
The former diplomatic service chief smiled awkwardly when it came to discussing Mr Johnson, before describing him as “chaotic”.
Sir Simon played a small role in bringing down the prime minister earlier this year when he said No 10 was “not telling the truth” about what Mr Johnson about Tory MP Chris Pincher, accused of sexual misconduct.
The former top civil servant, who ran the Foreign Office at the time a complaint was made against Mr Pincher, said Downing Street “keeps changing their story and are still not telling the truth”.
Although he did not work under Liz Truss, Lord McDonald said he thought she was an even “worse prime minister than Boris Johnson” and made “two immediate, irrevocable mistakes”.
He said: “The first was excluding from her government anybody who had supported her to the hilt.
“The second was running a mini-Budget that was ideologically driven, and before launching that Budget take care to make sure she could not hear, would not receive, any contrary advice.”