Donald Trump has attacked James Comey, describing him as a "showboat" and a "grand-stander" in an interview seeking to justify his shock decision to fire his FBI director.
The president also directly contradicted the narrative spun by his White House that he had fired Mr Comey following the urgent recommendation from the justice department.
"He's a showboat, he's a grand-stander, the FBI has been in turmoil," Mr Trump said in an interview with NBC News. "You know that, I know that. Everybody knows that."
He also admitted the Russia investigation was on his mind when he decided to fire him.
"In fact when I decided to just do it, I said to myself, I said you know, this Russia thing with Trump and Russia is a made-up story, it's an excuse by the Democrats for having lost an election that they should have won," he said.
Comey refused to pledge loyalty to Trump
Mr Trump's character assassination came as associates of Mr Comey said the president summoned Mr Comey to the White House two weeks after his inauguration and asked him to pledge his loyalty to him.
The FBI director declined to make that pledge, it has been claimed, and told him instead that he would be “honest” but not “reliable” in the political sense.
The former FBI director believes it was his reluctance to pledge loyalty that led to his eventual dismissal on Tuesday, two people who have heard Mr Comey’s account of the meeting told the New York Times.
The White House disputes that account, claiming it was Mr Comey who requested the dinner and the issue of loyalty never arose.
Trump 'declared war on FBI'
Officials in the FBI are seeking to defend the reputation of their former boss, setting up the potential for, what one informed source termed a "war", between the White House and the bureau.
Speaking before the Senate Intelligence Committee, Andrew McCabe, the Acting FBI Director, declared it the "greatest privilege" of his career to have served with Mr Comey.
The president's letter firing Mr Comey, and accompanying memos from the attorney general's office asserted that he was not capable of leading the bureau, and the White House suggested that he had lost the confidence of its staff.
"That's not accurate," Mr McCabe said. "I can tell you that Director Comey enjoyed broad support within the FBI, and still does to this day."
Mr McCabe's testimony was echoed by the heads of two associations representing current and retired FBI agents and other personal.
“His support within the rank and file of the FBI is overwhelming,” Thomas O'Connor, a working FBI special agent who is president of the FBI Agents Association told Politico.
One official told the Washington Post that Mr Trump had “essentially declared war on a lot of people at the FBI,” and that "there will be a concerted effort to respond".
Trump 'asked Comey three times' if he was under investigation
The president was reported to have been growing increasingly frustrated with the FBI's ongoing investigation into allegations of collusion between his associates and Russia.
Mr McCabe, the Acting Director, long involved in the Russia investigation, told the Senate Intelligence Committee that the inquiry would continue despite Mr Comey's dismissal.
He also said he would refrain from giving the White House updates on it, and would tell Congress if there was any attempt to impede the probe.
He starkly disagreed with the White House's characterisation of the Russia investigation being "probably one of the smallest things" on the FBI's plate.
"We consider it to be a highly significant investigation," he said. "You cannot stop the men and women of the FBI from doing the right thing."
Mr Trump said on Thursday that he had asked Mr Comey directly if he was being investigated, noting that he spoke with Comey once over dinner and twice by phone.
"I said, if it's possible would you let me know, 'Am I under investigation? He said, 'You are not under investigation'."
Mr McCabe declined to confirm in his testimony whether he had ever heard Mr Comey telling Mr Trump that the president was not a target of the investigation.
Chuck Grassley, the Republican chairman of the Senate Judiciary Committee, called on the FBI to say publicly whether it is investigating Mr Trump.
“Because it has failed to make this clear, speculation has run rampant," he said. “Wild speculation that the FBI is targeting the president in a criminal or intelligence inquiry is not just irresponsible and unfounded."
The comments came as the White House scrambled to create a coherent public narrative for the sacking.
In the immediate aftermath of the dismissal - marking only the second time an FBI director has been dismissed in the agency's 109-year history - it said Mr Trump had followed the recommendations of the justice department.
Rod Rosenstein, who had been in post for two weeks, wrote a three-page memo criticising the way Mr Comey had handled the investigation into Hillary Clinton's emails, but stopped short of recommending the dismissal of the FBI Director.
On Thursday informed sources said Mr Rosenstein had threatened to resign, incensed that he was being cast as the prime mover for the decision.
Trump 'was going to fire Comey regardless'
Pres. Trump on firing Comey: "I said, you know, this Russia thing with Trump and Russia is a made up story." https://t.co/hxqM1LI6BE— NBC Nightly News (@NBCNightlyNews) May 11, 2017
And Mr Trump confirmed that he had long been planning to fire Mr Comey.
"I was going to fire Comey," Mr Trump said. "Regardless of recommendation I was going to fire Comey."
For a president obsessed with loyalty, Mr Trump took the former FBI Director's recent testimony that he had felt "mildly nauseous" that his investigation into Hillary Clinton's emails could have influenced in the election, as a personal affront.
The dislike was mutual, with Mr Comey privately describing the President as “outside the realm of normal,” and even “crazy," according to sources cited by the New York Times.
Sarah Huckabee Sanders, the White House deputy press secretary, said Mr Comey's testimony to the Senate committee last week was the "final straw that pushed" the president to fire him.
She said Mr Rosenstein's memo "solidified" his decision.
She added: "I've heard from countless members of the FBI that are thankful and grateful for the president's decision. I'm sure some people will be disappointed. But I've heard from a large number of individuals and I don't even know that many people in the FBI."
"The president knew Mr Comey was not up to the task. He wanted someone to bring credibility back to the FBI."
Shortly before Mr Trump's remarks were broadcast Mr Rosenstein requested a meeting with the leaders of the Senate Intelligence Committee where he arrived with a security detail.
Following the meeting Mark Warner, the Democrat vice-chairman of the committee, said: "I voted to confirm this individual as deputy attorney general. I was disappointed. I still find the timing of the dismissal very troubling. I expressed that to Mr Rosenstein. He took it under advisement, he listened."
Chuck Schumer, the Democrat leader in the Senate, said Mr Rosenstein's reputation as an ‘‘independent, apolitical actor" was at risk unless he begins sharing details of how the decision to fire Mr Comey was made.
Mr Schumer said: "Over the last three decades of your career at the Department of Justice, you have developed a reputation for integrity and impartiality. That reputation is now imperiled by your participation in the abrupt dismissal of FBI Director Comey."
Russia must be laughing up their sleeves watching as the U.S. tears itself apart over a Democrat EXCUSE for losing the election.— Donald J. Trump (@realDonaldTrump) May 11, 2017
Mr Trump's comments also appeared to have alienated the leadership of the Senate intelligence committee, which is investigating Russian meddling in the election.
Senator Richard Burr, the Republican committee chairman, said: "I found him (Director Comey) to be one of the most ethical, upright, straightforward individuals I have had the opportunity to work with.
"The lion's share of FBI employees respect the former Director and that shows the professionalism he brought to the role."
Senator Mark Warner, the Democratic committee vice chairman, said he was "offended" by Mr Trump's comment that Mr Comey was a "showboater".