EXPLOSIVE evidence that threatened to undermine Donald Trump’s presidency has been delivered by former FBI director James Comey, who said the president fired him to interfere with his investigation into Russia’s role in last year’s election and its ties to Trump’s campaign. Comey told the Senate intelligence committee under oath: “It’s my judgment that I was fired because of the Russia investigation. I was fired in some way to change... the way the Russia investigation was being conducted.”

He also accused the Trump administration of spreading “lies, plain and simple” about him and the FBI after his abrupt sacking last month, declaring that the administration “defamed him and more importantly the FBI” by claiming the bureau was in disorder under his leadership.

And in testimony that exposed deep distrust between himself and the president, he described his discomfort about their one-on-one conversations, saying he decided he immediately had to document the discussions in memos.

“I was honestly concerned that he might lie about the nature of our meeting, so I thought it really important to document,” said Comey. “I knew there might come a day when I might need a record of what happened not only to defend myself but to protect the FBI.”

The revelations came as Comey delivered the first public airing of his relationship with Trump at a packed committee hearing.

He went straight to the heart of the political controversy around his sacking and whether Trump interfered in the FBI’s Russia investigation, as he elaborated on written testimony delivered on Wednesday.

In that, he disclosed that Trump demanded his “loyalty” and pushed him to “lift the cloud” of investigation by declaring publicly that he was not the target of the FBI probe into his campaign’s Russia ties.

Comey said he declined to do so in large part because of the “duty to correct” that would be created if that situation changed.

He also said in his written testimony that the president, in a strange private encounter in the Oval Office, pushed him to end his investigation into former national security adviser Michael Flynn.

Democratic Senator Joe Manchin asked Comey the key question: “Do you believe this arises to obstruction of justice?”

“I don’t know. That’s Bob Mueller’s job to sort that out,” Comey responded, referring to the newly appointed special counsel who has taken over the Justice Department’s Russia probe.

In a startling disclosure, Comey revealed that after his sacking he had tried to spur the special counsel’s appointment by giving one of his memos about the president to a friend of his to leak to the press.

“My judgment was I need to get that out into the public square,” he said.

The Republican National Committee and other White House allies have tried to lessen any damage from the hearing, bidding to undermine Comey’s credibility by issuing press releases and even adverts pointing to a past instance where the FBI had had to clean up his testimony to Congress. Trump is expected to dispute Comey’s claims that he demanded loyalty and asked him to drop the Flynn probe.

The president has not yet publicly denied the specifics of Comey’s accounts but has challenged his credibility, tweeting last month that he “better hope there are no ‘tapes’” of the conversations.

“Lordy, I hope there are tapes,” Comey remarked at one point yesterday, suggesting they would back up his account over any claims from Trump.

But it was Democrat Senator Dianne Feinstein who asked the question many Republicans have raised since Comey’s sacking as media leaks revealed his claims about Trump’s inappropriate interactions with him.

Discussing the Oval Office meeting, Feinstein asked: “Why didn’t you stop and say, ‘Mr President, this is wrong,’?”

“That’s a great question,” Mr Comey said. “Maybe if I were stronger I would have. I was so stunned by the conversation I just took it in.”

Comey asserted the intelligence community’s conclusion that Russia had meddled in the 2016 election: “There should be no fuzz on this. The Russians interfered... It’s about as unfake as you can possibly get.”