Donald Trump has slammed ex-FBI director James Comey as an "untruthful slime ball" in response to a series of explosive claims and personal barbs made about the President in his new book.
Excerpts from A Higher Loyalty: Truth, Lies and Leadership have been made public ahead of its release next week, with the former intelligence chief blasting his old boss as "unethical" and "untethered to the truth".
The book includes a number of damning assessments of Mr Trump's presidency and character, much like the publication of journalist Michael Wolff's Fire and Fury from earlier this year.
Mr Trump has tweeted a furious retort to Mr Comey on Twitter, saying he had leaked "classified information" and "should be prosecuted".
He said: "James Comey is a proven LEAKER & LIAR. Virtually everyone in Washington thought he should be fired for the terrible job he did-until he was, in fact, fired.
"He leaked CLASSIFIED information, for which he should be prosecuted. He lied to Congress under OATH. He is a weak and untruthful slime ball who was, as time has proven, a terrible Director of the FBI.
"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 honor to fire James Comey!"
So what are some of the most damaging allegations to have angered the President?
More from Donald Trump
From observations about apparent fake tan lines to comparing the Trumps with a mafia crime family, Sky News looks at Mr Comey's more unflattering claims.