FBI director James Comey (left) and President Trump (right)
Nicholas Kamm, AFP/Getty Images

President Trump stepped up his unrelenting Twitter rant at former FBI director James Comey on Sunday, accusing him of "many lies" and dismissing the one-time federal prosecutor as the "WORST FBI director in history, by far!"

The attacks come hours before Comey's interview with ABC's George Stephanopoulos was scheduled to air Sunday night. The network has been promoting the interview with enticing bits of information, including Stephanopoulos revealing that Comey compares Trump to a “mob boss.”

Comey is promoting his new book to be released this week, Higher Loyalty: Truth, Lies, and Leadership. Leaked excerpts have detailed Comey's mistrust of Trump, whom he describes as "ego driven" and "untethered to truth."

"I never asked Comey for Personal Loyalty," Trump tweeted. "I hardly even knew this guy. Just another of his many lies. His “memos” are self serving and FAKE!"

More: Merriam-Webster saw a 60,000% increase in 'slimeball' searches

More: President Trump denounces James Comey as 'untruthful slime ball' 

Trump ripped Comey for acknowledging Democratic candidate Hillary Clinton's lead in the 2016 presidential polls was a factor in how he handled the controversial Clinton email inquiry. Comey announced weeks before the election that he would not recommend charges be filed for Clinton's handling of emails while secretary of State.

Days before the election, however, Comey acknowledged that he was reviewing additional information in the case.

“In other words, he was making decisions based on the fact that he thought she was going to win, and he wanted a job," Trump tweeted. "Slimeball!”

Former New Jersey governor Chris Christie chimed in, tweeting that when he worked for Comey, "if I had told him 11 days before an election that I was releasing information that could effect an election, and the decision was influenced by polling, he would have fired me. He would have fired me on the spot.

"He is guilty of doing that himself-Wow"

Trump abruptly fired Comey in May, and Trump's tweet summarizing his overall perspective on Comey comes as no surprise: "Slippery James Comey, a man who always ends up badly and out of whack (he is not smart!), will go down as the WORST FBI Director in history, by far!"

The attack on Twitter was essentially a continuation of Trump's tweets Friday, when he called Comey "a proven LEAKER & LIAR"  and a "untruthful slime ball."

"Virtually everyone in Washington thought he should be fired for the terrible job he did-until he was, in fact, fired," Trump tweeted Friday.

White House spokeswoman Sarah Sanders also took on Comey on Sunday during an appearance on ABC's This Week.

"Look, it's been very clear that James Comey is a self-admitted leaker," Sanders said. "He lied to Congress.  He's been inconsistent."

House Speaker Paul Ryan was somewhat more supportive of Comey, telling NBC's  Meet the Press  that Comey appeared to be a person of integrity. Ryan said, however, he had met Comey only a few times.

"I'm not going to try and help sell some books here," Ryan said. "I don't want to ... join some food fight, some book-selling food fight."