Former FBI Director James Comey's running feud with the president has continued after he labelled Donald Trump "morally unfit" for office.
In an interview with ABC News ahead of the release of his book, A Higher Loyalty, Comey detailed the events that led to his firing by the president last May.
When asked if he believed Mr Trump was fit to be president, he responded harshly.
"I don't buy the stuff about him being mentally incompetent, or early stages of dementia," he said.
"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."
Comey also said he believed that the president treated women like they're "pieces of meat", and that he lied constantly about matters "big and small".
Mr Trump and his party have been quick to retaliate to Comey's remarks.
Republican National Committee chairwoman Ronna McDaniel issued a statement following the interview, claiming that Comey's "true higher loyalty is to himself".
The president launched a tirade against Mr Comey before the program had even aired, branding him a "slimeball" and the "worst FBI director in history" in a series of angry tweets.
Comey revealed his version of incidents including Russian election meddling and investigations into Hillary Clinton's emails.
Back in March 2017, during an FBI investigation into Trump's campaign and alleged links to Russia, Comey claimed that he was asked to publicly state that the president was not being personally investigated.
This is something that the former FBI chief says he declined to do.
He added that it was "stunning" to think that Russia could hold damaging information about a US president.
Comey said that in Trump's case, it is not impossible that information about the president had been compromised in some way.
"These are more words I never thought I'd utter about a president of the United States, but it's possible," Comey said to ABC News' chief anchor George Stephanopoulos.
President Trump fired James Comey in May 2017, appointing Robert Mueller as special counsel to replace him.
Mueller is now investigating whether Trump obstructed the course of justice in firing the former FBI chief.
Mr Trump vehemently denies this allegation.
James Comey's controversial memoir, A Higher Loyalty: Truth, Lies, and Leadership, is set to be released this week.