Deputy Attorney General Rod Rosenstein is defending the memo he wrote outlining the problems with former FBI Director James Comey, in a statement he delivered to members of Congress this week.

The memo was touted as a formal justification for President Trump to fire Comey, but Rosenstein's statement to lawmakers said there were longstanding problems with Comey's actions, and that he wrote the memo after learning that Comey would be fired.

"Former Department of Justice officials from both political parties have criticized Director Comey's decisions. It was not just an isolated mistake; the series of public statements about the email investigation, in my opinion, departed from the proper role of the FBI Director and damaged public confidence in the Bureau and the Department," Rosenstein wrote.

He added that he met last year with then-Sen. Jeff Sessions, who has since become attorney general, to discuss the need for "new leadership at the FBI."

He also stressed that his memo "is not a statement of reasons to justify a for-cause termination," and that he stands by it. "I wrote it. I believe it. I stand by it," he wrote.

Rosenstein revealed that he learned President Trump intended to fire Comey on May 8, and sought his "advice and input" about it. Comey was subsequently terminated on May 9.

"Notwithstanding my personal affection for Director Comey, I thought it was appropriate to seek a new leader," Rosenstein wrote. "I wrote a brief memorandum to the Attorney General summarizing my longstanding concerns about Director Comey's public statements concerning the Secretary Clinton email investigation."

Rosenstein was at the Capitol on Friday to brief lawmakers at a closed-door meeting on both Comey's firing and his decision to appoint a special prosecutor to probe Russian interference in the 2016 election and possible collusion with the Trump campaign.