“He leaked CLASSIFIED information, for which he should be prosecuted. He lied to Congress under OATH.”

Comey said the president was also obsessed with the alleged existence of a video in which Russian prostitutes said to be hired by Trump urinated on the bed in a Moscow hotel room.

The allegations left Trump fuming.

“He is a weak and untruthful slime ball who was, as time has proven, a terrible Director of the FBI,” Trump added in a second tweet.

“His handling of the Crooked Hillary Clinton case, and the events surrounding it, will go down as one of the worst ‘botch jobs’ of history. It was my great honour to fire James Comey!”

In the book Comey says the US president lives in “a cocoon of alternative reality” that he tried to pull others around him into, according to The Washington Post.

Meetings with Trump gave Comey “flashbacks to my earlier career as a prosecutor against the mob”, he writes.

“The silent circle of assent. The boss in complete control. The loyalty oaths. The us-versus-them world view. The lying about all things, large and small, in service to some code of loyalty that put the organisation above morality and above the truth.”

But Comey goes farther to say that Trump, congenitally, has no sense of what is right and wrong.

“This president is unethical, and untethered to truth and institutional values,” he writes, according to The New York Times. “His leadership is transactional, ego driven and about personal loyalty.”

The book, titled A Higher Loyalty: Truth, Lies and Leadership, has triggered worries now rippling through the White House and Republican establishment over the damage it might do to the already deeply troubled Trump presidency.

The White House has sought to cast doubts about Comey’s reputation: the Republican Party this week put up a website called “Lyin’ Comey” to undermine the book. But among both Republicans and Democrats in Washington’s establishment, the reputation of Comey – who has served in the FBI under three presidents – is much stronger than his book’s target.

Last year, Comey revealed that Trump had pressured him to drop an investigation into Mike Flynn, the US leader’s former national security adviser, and also demanded a loyalty pledge.

Getting neither, the president fired Comey on May 9, complaining of the ongoing investigation into possible Trump campaign-Russia ties.

A week later the Justice Department appointed a special prosecutor Robert Mueller, who has doggedly pursued the probe as well as possible obstruction of justice by Trump. He has issued 19 indictments so far, including of top Trump lieutenants.

But A Higher Loyalty shares little new about the Russia investigation, with Comey bound to respect the classified nature of the Mueller investigation that Trump just this week labelled “fake and corrupt”.

According to the New York Post, Comey says Trump was obsessed with the “pee tape”, the existence of which was first reported by a former British intelligence agent who researched alleged links between Trump’s campaign and Russia.

Trump asked Comey to investigate “what he called the ‘golden showers thing’” Comey writes, saying Trump was determined to prove to his wife Melania that it did not exist.

“He just rolled on, unprompted, explaining why it couldn’t possibly be true, ending by saying he was thinking of asking me to investigate the allegation to prove it was a lie.”

But Trump’s concern over the alleged video extended to the numerous sex scandals that have dogged him over decades as a New York real estate tycoon – and have returned to haunt him in the White House.

In the past year two women, one a pornographic film star and the second a Playboy model, have said they were paid off to be silent about affairs they had with Trump over a decade ago while he was married to his current wife Melania.

Speaking on the Moscow video, Comey said, Trump “strongly denied the allegations, asking – rhetorically, I assumed – whether he seemed like a guy who needed the service of prostitutes.”

“He then began discussing cases where women had accused him of sexual assault, a subject I had not raised,” Comey wrote. “He mentioned a number of women, and seemed to have memorised their allegations.”