Donald Trump ran White House like a mafia boss, says former FBI director James Comey in new book

Former FBI director James Comey says in a new book that President Donald Trump reminded him of a mafia boss who demanded absolute loyalty, saw the entire world against him, and lied about everything.

According to excerpts of the book leaked by US media on Thursday, Trump 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.

File image of ex-FBI director James Comey. AP

In the book to be released officially next Tuesday, Comey, whom Trump fired in May 2017, 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."

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."

The book, entitled A Higher Loyalty: Truth, Lies and Leadership, has sparked worries through the White House and Republican establishment over the kind of damage it might do to the Trump presidency.

Last year, Comey revealed that Trump had pressured him to drop an investigation into Mike Flynn, Trump's former national security adviser, and also demanded Comey promise his loyalty.

Trump fired Comey on 9 May, complaining of the ongoing investigation into possible Trump campaign-Russia ties.

That firing led to the appointment of a special prosecutor, who continues to probe the issue as well as possible obstruction of justice and has issued 19 indictments so far, including of top Trump lieutenants.

Comey says in the book that Trump has no sense of what is true and what is not.

"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."