In his first interview since being fired by Mr Trump, Mr Comey said it was possible the Russians have compromising material on the US president.
Mr Comey portrayed Mr Trump as a serial liar who treats women like “meat” and acts like a mafia boss by demanding loyalty from those around him.
Mr Trump pre-empted the interview on Twitter on Sunday by saying Mr Comey was the “worst FBI director in history” and questioning his integrity.
Mr Comey headed up the FBI under Barack Obama and initially continued to work under Mr Trump before being fired on May 9 2017.
Obstruction of Justice
Mr Comey recounted a meeting with Mr Trump in the Oval Office on February 14 2017 in which he believes obstruction of justice may have taken place.
Mr Trump asked all those present including Mike Pence, the vice president, and Jeff Sessions, the attorney general, to leave the room except for Mr Comey.
“I didn't know what was going to happen next, but I knew that whatever it was, it was really, really important that I remember everything that was said,” Mr Comey said.
Mr Comey recalled that Mr Trump urged him to drop an investigation into Michael Flynn, his former national security adviser whose connections with the Russian ambassador were under scrutiny.
He recalled Mr Trump saying: “He's a good guy, I hope you can let it go.” Mr Comey said his response was simply “he's a good guy”.
Asked what he was thinking at the time, Mr Comey said: “He's asking me to drop the criminal investigation of his, now former, national security adviser.”
Asked if Mr Trump was “obstructing justice”, Mr Comey responded: “Possibly. I mean, it's certainly some evidence of obstruction of justice.”
The comment is significant as obstruction of justice is one of the grounds for bringing impeachment charges against a sitting president.
It is also an area that Robert Mueller, the special counsel, is believed to be investigating.
Trump 'morally unfit' for presidency
Mr Comey was clear that he considered Mr Trump to be “morally unfit” to lead the country, citing his comments on the white nationalist protests in Charlottesville, Virginia.
Asked if Mr Trump was unfit to be president, Mr Comey said: “Yes. But not in the way I often hear people talk about it.
“I don't buy this stuff about him being mentally incompetent or early stages of dementia. He strikes me as a person of above average intelligence who's tracking conversations and knows what's going on.
“I don't think he's medically unfit to be president. I think he's morally unfit to be president.
“A person who sees moral equivalence in Charlottesville, who talks about and treats women like they're pieces of meat, who lies constantly about matters big and small and insists the American people believe it, that person's not fit to be president of the United States, on moral grounds.”
Read the original article on the Telegraph.
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