Washington (CNN) Former FBI Director James Comey slammed Republicans on Monday for not speaking out against President Donald Trump's attacks on the FBI and strongly defended the agency's conduct, following his second round of questioning at a closed-door congressional interview.

"Somebody has to stand up and speak for the FBI," Comey told reporters after his nearly six-hour interview with members of the House Judiciary and Oversight committees. "People who know better, including Republican members of this body, have to have the courage to stand up and speak the truth, not be cowed by mean tweets or fear of their base. There is a truth and they're not telling it. Their silence is shameful."

Comey's comments came after he spent more than five hours behind closed doors on Monday with Republicans and Democrats. He was questioned on the FBI's handling of both the Hillary Clinton email investigation and the Russia investigation.

Comey issued a fiery and defiant statement as he left Monday, charging Trump and Republicans with damaging the FBI's reputation and asserting that "damage has nothing to do with me."

"The FBI's reputation has taken a big hit because the President of the United States has lied about it constantly," Comey said.

Behind closed doors, Comey defended the FBI, saying he and the bureau made the right call in 2017 when he rebuffed Trump's requests to announce publicly that the President wasn't under investigation, a source familiar with the interview told CNN.

Under questioning from Democrats, Comey said that he didn't want to declare publicly that Trump wasn't under investigation because of a concern that the situation could change and the FBI would have to make another announcement. And he told lawmakers that he was proven right because it now appears Trump was in fact under investigation, the source said, though Comey said that he was only basing that from public reporting and not any inside knowledge.

White House press secretary Sarah Sanders responded to Comey's comments by tweeting Monday evening: "Republicans should stand up to Comey and his tremendous corruption - from the fake Hillary Clinton investigation, to lying and leaking, to FISA abuse, and a list too long to name. The President did the country a service by firing him and exposing him for the shameless fraud he is."

Flynn's FBI interview under scrutiny

Comey also defended the FBI's interview with former national security adviser Michael Flynn, who was later charged with lying in the January 2017 interview, and he slammed Trump's labeling his former attorney Michael Cohen a "rat."

"This is the President of the United States calling a witness, who has cooperated with his own Justice Department a rat," Comey said. "We have to stop being numb to it; whether you're Republican or Democrat, stand on your feet, overcome your shame and say something."

Republicans had a different view of Comey's interview, not to mention his tenure as FBI director, raising questions about his handling of the opposition research dossier on Trump and Russia among other topics, including the January 2017 FBI interview with Flynn.

North Carolina Republican Rep. Mark Meadows said going into the Comey interview Monday that he felt there were inconsistencies in the former FBI director's testimony earlier this month.

"I think that the knowledge of when the FBI and specifically Director Comey became aware of the involvement of the DNC, Perkins Coie, Fusion GPS as it relates to their hiring of Christopher Steele, the whole FISA application. At what point did he become aware of that?" Meadows said.

"He seemed to indicate the other day that he wasn't aware of that until he read reports long after he was gone," Meadows added. "I find that very hard to substantiate based on other evidence. So hopefully we'll give him a chance today to clarify that. I can tell you when you look at his public statements and also his testimony, those don't seem to reconcile, so we're going to give him a chance to hopefully reconcile his remarks."

Republicans spent the first part of Monday's interview with a lengthy discussion on the FBI's interview with Flynn, which eventually led to his charges by special counsel Robert Mueller. The Republican questioning over Flynn was going on at the same time Monday that charges were announced by the Justice Department against two of Flynn's associates, according to the source familiar with the interview.

After the interview, Comey defended the FBI's interview with Flynn, including his decision not to inform then-acting Attorney General Sally Yates about it ahead of time.

"Oh come on. Think about what's happening in the Republican Party. They're up here, attacking the FBI's investigation of a guy who (pleaded) guilty to lying to the FBI," Comey said when asked to respond to the criticism. "I'm very proud of the way the FBI conducted itself."

Comey returns

Comey sat down with lawmakers from both parties for another six-hour interview earlier this month. The committees are also interviewing former Attorney General Loretta Lynch behind closed doors on Wednesday.

Monday's sequel with Comey was odd in at least one respect because the 235-page transcript of the first part of Comey's interview was released the day after he testified, giving the public an opportunity to Monday-morning quarterback the proceedings before they concluded.

Republicans left that previous interview saying they were frustrated with the questions that Comey couldn't answer, and they noted after the interview how many times Comey had responded that he did not know or recall an answer to their questions.

But Democrats have criticized bringing Comey back. Rep. Lacy Clay, a Democratic member of the House Oversight Committee, called the interview so far a waste of time, saying it amounted to the "last gasp" of the Republican majority.

Trump also took the opportunity to weigh in on Twitter to attack Comey and the special counsel investigation.

"Leakin' James Comey must have set a record for who lied the most to Congress in one day," Trump tweeted last week, without providing evidence for his claim. "His Friday testimony was so untruthful! This whole deal is a Rigged Fraud headed up by dishonest people who would do anything so that I could not become President. They are now exposed!"

Comey offered his own assessment after the first round of questions had concluded, tweeting that the interview "wasn't a search for truth, but a desperate attempt to find anything that can be used to attack the institutions of justice investigating this president. They came up empty today but will try again. In the long run, it'll make no difference because facts are stubborn things."

Last chance for House GOP

Comey's two interviews are part of the Republican-led congressional investigation into the FBI's conduct during the 2016 investigations into Hillary Clinton's email and Russia.

The interviews with Comey and Lynch are likely to be among the last for the Republican-led investigation, as incoming Judiciary Chairman Jerry Nadler, D-New York, has already made clear he has no interest in continuing the Republican FBI probe once Democrats take control of the House.

Gowdy and outgoing Judiciary Chairman Bob Goodlatte are also retiring from Congress. They haven't yet said what they plan to do to summarize their findings in the yearlong investigation into the FBI and Justice Department.

In the transcript of Comey's interview earlier this month, the former FBI director defended the FBI's investigations as well as Mueller's integrity.

"There are not many things I would bet my life on. I would bet my life that Bob Mueller will do things the right way, the way we would all want, whether we're Republicans or Democrats, the way Americans should want," Comey said.

Much of the content of the interview was similar to the questions that the Justice Department inspector general probed in a report released earlier this year that faulted Comey for his actions in the Clinton email case.

Comey was quizzed about his interactions with Trump and a potential obstruction of justice case that would involve Trump's comments to him about the investigation into Flynn.

There also were some tidbits in the interview about the Russia investigation, a topic in which an FBI lawyer limited what Comey could discuss.

But Comey, for instance, said that the FBI's counterintelligence investigation opened in July 2016 was an investigation into four individuals and not the Trump campaign itself.

New information about Flynn interview, dossier

The two-part interview has one benefit for lawmakers: Two new documents have been released since Comey last appeared earlier this month.

The FBI on Friday released a redacted version of the memo that Comey and other top intelligence officials used to brief Trump about the dossier in January 2017. The memo discloses how Steele was described, and Republicans are likely to press Comey on why it didn't include the fact he was paid by Democrats.

In addition, the special counsel's office last week released memos from the FBI about Flynn's interview when he lied about the content of calls with then-Russian ambassador to the US Sergey Kislyak.

The memos were released to push back on an assertion from Flynn's attorneys that the FBI caught Flynn off guard with the January 2017 interview.

They're also relevant to Comey's congressional testimony, as lawmakers asked him about his assessment of the FBI's interview with Flynn during Comey's first round of testimony. Trump and some Republicans have also suggested that the FBI didn't initially believe Flynn lied after the interview.

"They gave General Flynn a great deal because they were embarrassed by the way he was treated - the FBI said he didn't lie and they overrode the FBI," Trump tweeted Thursday. "They want to scare everybody into making up stories that are not true by catching them in the smallest of misstatements. Sad!"

Peter Strzok, the FBI agent who was fired over anti-Trump text messages, wrote that the agents who interviewed Flynn had "the impression that Flynn was not lying or did not think he was lying." But the memos did not say whether the FBI made any judgments that day about whether Flynn was lying.

And Comey pushed back on that notion in his testimony.

"My recollection was he was -- the conclusion of the investigators was he was obviously lying, but they saw none of the normal common indicia of deception: that is, hesitancy to answer, shifting in seat, sweating, all the things that you might associate with someone who is conscious and manifesting that they are being -- they're telling falsehoods," Comey said. "There's no doubt he was lying, but that those indicators weren't there."

This story has been updated with developments throughout Monday.