US President Donald Trump has attacked former FBI director James Comey as a "weak and untruthful slime ball", reacting to news accounts that cite Mr Comey as hugely critical of the President in a memoir due to be published next week.

Key points: Mr Comey's book reportedly paints a deeply unflattering portrait of Mr Trump

Mr Comey's book reportedly paints a deeply unflattering portrait of Mr Trump Mr Trump fired the former FBI director last May

Mr Trump fired the former FBI director last May Mr Comey has accused the Trump administration of lying and defaming him

"It was my great honour to fire James Comey!" Mr Trump said in a series of angry tweets, adding he had been a "terrible" FBI director.

Mr Trump fired Mr Comey last May and has publicly criticised him since then, but not to this extent.

Mr Trump's attack reflected months of simmering anger against a career law enforcement bureaucrat who has emerged as one of his fiercest opponents.

Mr Comey had been investigating allegations that Russia meddled in the 2016 presidential election and possible collusion between Russians and the Trump campaign.

His firing led to the Justice Department appointing Special Counsel Robert Mueller to take over the Russia investigation.

Mr Trump has denied any collusion, but the Russia probe has been hanging over his presidency.

"James Comey is a proven LEAKER & LIAR," Mr Trump tweeted.

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He also accused Mr Comey of lying to Congress, apparently referring to Mr Comey's Senate testimony last June, when he said he needed to get his account of his conversations with Mr Trump in the public sphere in the hope it might prompt the appointment of a special counsel.

Mr Comey told politicians he had given copies of his memo detailing his talks with Mr Trump to people outside the Justice Department and asked a friend to share its contents with a journalist.

The former FBI director is doing a series of media interviews before the release of his book, A Higher Loyalty: Truth, Lies and Leadership, which reportedly paints a deeply unflattering picture of the President being "untethered to truth".

The interviews are Mr Comey's first public comments since he testified before the Senate Intelligence Committee last June, when he accused Mr Trump of firing him to undermine the FBI's Russia investigation.

Mr Comey said at the time the Trump administration had lied and defamed both him and the FBI after he was dismissed on May 9.

Trump wanted investigation into Russian prostitutes claim

In an interview broadcast on Friday on US ABC program Good Morning America, Mr Comey discussed his initial encounters last year with the new President.

He described Mr Trump as volatile, defensive and concerned more about his own image than about alleged Russian meddling in the presidential election.

Mr Comey said he cautioned Mr Trump against ordering an investigation into a salacious intelligence dossier alleging Russian agents videoed Mr Trump with prostitutes urinating on each other in a Moscow hotel room in 2013.

In the book, Mr Comey wrote that Mr Trump raised the intelligence dossier with him at least four times during meetings after Mr Trump took office in January, according to the Washington Post, which obtained a copy.

The dossier looking at Mr Trump's alleged ties to Russia was compiled by former British intelligence officer Christopher Steele

James Comey said Donald Trump was worried his wife Melania would believe allegations involving Mr Trump and prostitutes. ( AP: Carolyn Kaster )

Mr Trump denied the allegations and said he might want the FBI to investigate them to prove they were not true, Mr Comey said.

"I said to him, 'Sir that's up to you but you want to be careful about that because it might create a narrative that we're investigating you personally and, second, it's very difficult to prove something didn't happen," Mr Comey said.

He said Mr Trump was worried there was a chance his wife, Melania Trump, would believe the allegations.

In the book, Mr Comey reportedly writes that that he asked himself: "Why his wife would think there was any chance, even a small one, that he had been with prostitutes urinating on each other in a Moscow hotel room".

Mr Comey said he told the President the FBI had not proved or disproved the allegations but thought it was important Mr Trump knew about them.

Mr Comey said the allegations in the dossier had not been verified at the time he left the FBI. He said he did not know whether the events described in the dossier were true.

He said the President asked him: "Do I look a guy who needs hookers?". Mr Comey added that he "assumed he was asking that rhetorically".

'Almost an out of body experience'

Asked how bizarre that meeting with Mr Trump was, Mr Comey said: "Very weird. Really weird. It was almost an out of body experience for me. I was floating above myself looking down saying 'you're sitting here briefing the incoming president of the United States about prostitutes in Moscow'."

What struck him most, Mr Comey told ABC, was that the conversation moved straight into a public relations mode, what they could say and how they would position Mr Trump.

"No one, to my recollection, asked what's coming next from the Russians, how might we stop it, what's the future look like," Mr Comey said.

Moscow has repeatedly denied that it interfered in the 2016 campaign in hopes of tilting the election in Mr Trump's favour.

Reuters/ABC