Donald Trump’s constant need for affirmation makes the next few days a dangerous time in the United States, former FBI director James Comey has warned.

Mr Comey, who was fired by Mr Trump in 2017, called the outgoing President a “demagogue” who has a “menace” to him in private similar to that of a mob boss.

He said there are tens of millions of people in the US caught up in a “fog of lies” about Covid-19, the election and the country’s institutions, and he said Mr Trump aimed to “destroy the notion that truth exists”.

Appearing on Sky News’ Sophy Ridge On Sunday programme, Mr Comey was asked how worried he is about more violence in the coming days or weeks, particularly around Joe Biden’s inauguration on Wednesday.

He said: “I’m worried because there are armed, disturbed people who are in this state of mind where they believe that their country is being taken from them, and so it’s a threat law enforcement in the States has to take very seriously.

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“At the same time, I know that we have the capability, investigative and the tactical capability on scene, to protect these locations and so I’m optimistic that the threat will be neutralised, but it has to be taken very, very seriously.”

Mr Comey was asked about what Mr Trump is like and how he will cope with not being in office any more.

He said: “I have never seen an adult with a greater hunger for affirmation than Donald Trump.

“I’ve seen it in two-year-olds and three-year-olds.

“Affirmation is like air – he needs it constantly, which is what makes the next seven days or so so dangerous in the States, because he feels the affirmation slipping away and no doubt feels betrayal by those around him.

James Comey in DublinJames Comey accused Donald Trump of telling a number of lies (Brian Lawless/PA)

“It’s striking to encounter a human being, especially in a leadership role, with that hunger.

“Then there’s one other piece that people don’t often see – there’s a menace to him in private that you don’t pick up in public and I have felt it sitting close to him, that constantly reminded me of a mob boss because I’ve known mob bosses and helped put them in jail.

“That menace, coupled with that hunger for affirmation, is a really dangerous recipe.”

Mr Comey said Mr Trump is “the dictionary definition of a demagogue – a populist demagogue willing to say anything at any moment to try to whip people up to support him”.

During the interview, which took place on Wednesday, he said: “It’s been extraordinary. The press, to its great credit, has tried to keep track of his lies and communicate about them, but lying works.

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“It’s the reason a demagogue was the great fear of the designers of the American Republic. Lying works.

“We can’t ever kid ourselves that it’s ineffective. It’s effective and that’s why all of us have to fight back against it.”

Foreign Secretary Dominic Raab was separately asked on the same programme if he was looking forward to Mr Trump leaving office.

He replied: “It’s the job of the British Government, and certainly as Foreign Secretary, to make the best of our relations with whoever’s in the White House.

“I think we’ve seen some pretty shocking scenes in terms of Capitol Hill recently, the Prime Minister has been very clear on all of that.”

Mr Raab said the Government was focused on working with a new US administration on issues such as human rights, Covid-19 and climate change.