One memo said Trump asked Comey to shut down an investigation into Flynn, who eventually admitted lying to the FBI about conversations with Russia's ambassador.
The admission led to one of the earliest indictments to come from special counsel Robert Mueller's investigation into contacts between Russia and the Trump 2016 election campaign. The Justice Department's Office of Inspector General berated Comey for asking an acquaintance teaching at Columbia University to share the contents of the memo with The New York Times.
Comey set a "dangerous example" for FBI employees in an attempt to "achieve a personally desired outcome," the report states. But it found "no evidence that Comey or his attorneys released any of the classified information contained in any of the memos to members of the media" and said prosecutors had declined to bring a case.
Comey, who was among 17 people interviewed by the IG's office for the investigation, immediately responded on Twitter, saying a "quick message with a 'sorry we lied about you' would be nice."
Comey singled out the president, who has repeatedly upbraided the former intelligence official as a "leaker" since details of the memos emerged.
"And to all those who've spent two years talking about me 'going to jail' or being a 'liar and a leaker' - ask yourselves why you still trust people who gave you bad info for so long, including the president," Comey said.
The IG focused on Comey's handling of seven memos detailing interactions with Trump in the first three months of 2017. Comey kept signed originals of four memos at home after being fired, without telling the FBI.