In his second tweet, Trump - who frequently resorts to name-calling others who ruffle his feathers - described the former director as an "untruthful slime ball", adding, "It was my great honor to fire James Comey!".
In the book, which is available April 17, Comey also reveals new details about how the government had unverified classified information that he believes could have been used to cast doubt on Attorney General Loretta Lynch's independence in the Clinton probe. "He lied to Congress under OATH".
With the upcoming release of his book, "A Higher Loyalty: Truth, Lies, and Leadership", Comey is back in the spotlight.
The interviews are Comey's first public comments since he testified before the Senate Intelligence Committee last June, when he accused Trump of firing him to undermine the FBI's Russian Federation investigation.
White House press secretary Sarah Sanders also attacked Comey's credibility Friday.
"I said to him, 'Sir that's up to you but you want to be careful about that because it might create a narrative that we're investigating you personally and, second, it's very hard to prove something didn't happen, '" Comey said.
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Comey writes that Obama told him in a White House meeting after the election, "I picked you to be Federal Bureau of Investigation director because of your integrity and your ability". With each Stephanopoulos question, they cut back to Comey and the drama builds as we want to know what Comey's responses are going to be.
"James Comey is a proven LEAKER & LIAR", Trump wrote.
The book is due to be released on Tuesday, but Comey has already appeared on television to promote it and the White House has been strategising for weeks about how to discredit it. I have read [Hillary Clinton] has felt anger toward me personally, and I'm sorry for that.
"He just rolled on, unprompted, explaining why it couldn't possibly be true, ending by saying he was thinking of asking me to investigate the allegation to prove it was a lie".
The pair are engaged in an explosive showdown with Mr Comey's first major interview with ABC News scheduled to be broadcast on Sunday evening in the United States.
In an excerpt shown on Saturday, Comey said his belief that Hillary Clinton would win the 2016 presidential election was a factor in his decision to disclose the investigation into her emails. He recalled telling Trump about the dossier at a meeting in Trump Tower.
Trump offered varying explanations to convince Comey it was not true.
After Clapper briefed the team on the intelligence community's findings of Russian election interference, Comey said he was taken aback by what the Trump team didn't ask.