In this memo, McCabe, who was sacked by Trump in March, described a conversation last May with Deputy Attorney General Rod Rosenstein about a memo Rosenstein was drafting about Comey's mismanagement of the F.B.I.
That was a departure from the White House's original rationale for the firing: that Comey was compromised because of incompetence in handling the 2016 probe into Hillary Clinton's private email server.
A representative for McCabe declined to comment for this story, and a Justice Department spokeswoman did not immediately respond to a request for comment.More news: Controversial burqa ban now a reality
Two days after firing James B. Comey as Federal Bureau of Investigation director, Trump told NBC News" Lester Holt: "And, in fact, when I made a decision to just do it, I said to myself, I said: "You know, this Russian Federation thing with Trump and Russian Federation is a made-up story".
"I just want somebody that's competent", Trump said.
According to the Times story, McCabe believed that Rosenstein may have been providing a cover story for Trump, and that Comey's firing was in fact impelled by the Russian Federation investigation. Mr. Rosenstein said it was unnecessary and did not include such a reference.More news: Abramovich's Chelsea suspends $1.3b stadium plans
Trump ended up shelving that letter in favor of a far shorter one, but the draft has taken on new significance in the probe by special counsel Robert S. Mueller III, who is examining it as he determines whether Trump's firing of Comey was part of an effort to obstruct justice, according to people with knowledge of the investigation.
Rosenstein took notes about the exchange, according to the Times' sources.
Questions have been raised over Deputy Attorney General Rod Rosenstein's future after a report on Wednesday disclosed the contents of a memo that suggested he may have provided cover for President Donald Trump to fire FBI Director James Comey. One wonders whether a conversation with one of his lawyers or a "Fox & Friends" discussion about obstruction of justice might have prompted such a self-serving tweet.More news: Jorginho 'agrees five-year Manchester City deal'
The president's assertion, in a morning tweet, is at odds with comments he made in a television interview past year in which he said Comey's stewardship of the Russian Federation probe was on his mind when he made his decision to dismiss him. This evidence should have been collected a year ago, and likely was, when Mueller first got appointed special counsel.