"Thank you for providing even more material for the defamation suit we are actively considering filing against you and your colleagues".
In a statement, Mr. McCabe said that he had full authorization to share this information with the media.
Mr. Trump responded to Comey's book for the first time Friday, calling him a "LEAKER & LIAR" and saying he "should be prosecuted".
The inspector general said that when investigators asked whether he had instructed aides to provide information in October 2016 to a reporter with The Wall Street Journal, Mr. McCabe said he did not authorize the disclosure and did not know who did. "LIED! LIED" and was "totally controlled" by Comey, whom Trump fired last May as the FBI was investigating possible collusion between the Trump campaign and the Russians.
That may not matter to Mr Trump, who sees the executive offices of the Federal Bureau of Investigation as a "den of thieves and lowlifes" akin to a law-enforcement version of the fictional Star Wars' Mos Eisley cantina.
Mr McCabe's lawyer said in a statement his client was unfairly treated and the inspector general rushed to finish the report before he could retire.More news: Man robs bank hoping to get Taylor Swift's attention
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In addition to Comey, Trump is pushing back against claims that he had extramarital affairs with porn star Stormy Daniels and Playboy playmate Karen McDougal.
The attorney general, Jeff Sessions, dismissed him last month, two days before his scheduled retirement, for what he described as a lack of candor.
The Associated Press has also confirmed that McCabe kept personal memos detailing interactions with the president and they have been provided to the special counsel's office.
Before firing McCabe, Trump had zeroed in on contributions a political group aligned with then-Virginia Gov. Terry McAuliffe (D) made to McCabe's wife's unsuccessful campaign for state senator in 2015.
The inspector general, in contrast, found that McCabe violated FBI policy by acknowledging the existence of a criminal investigation that was not public at the time.
McCabe has also said he believes he was singled out because of the "role I played, the actions I took, and the events I witnessed in the aftermath" of Comey's firing. It was Mr McCabe's word against Mr Comey's, and the inspector general sided with the latter.
That investigation is looking into Russian interference in the 2016 presidential election, possible collusion between the Trump campaign and the Kremlin, and possible obstruction of justice by the president.