"This is the president of the United States calling a witness who is cooperating with his own Justice Department a 'rat.' Say that again to yourself at home and remind yourself where we have ended up," Comey said, referring to a tweet from the president calling his former personal attorney Michael Cohen a "rat."
Cohen was sentenced to various crimes including campaign finance violations, tax evasion and lying to Congress after flipping on his former boss and cooperating in multiple investigations.
"Republicans used to understand that the actions of a president matter, the words of a president matter, the rule of law matters and the truth matters," Comey said, taking a more political tone Monday afternoon than he did last Friday following his first round of testimony in front of the House Judiciary and Oversight committees. "Where are those Republicans today? At some point, someone has to stand up."
Comey said questions during the closed-door hearing once again focused on Hillary Clinton's email server and the Christopher Steele dossier.
"I find it frustrating to be here answering questions about things that are far less important than the values this country is built upon," he said.
When asked if he thought Monday's testimony was useful or merely a political maneuver by House Republicans, Comey said he couldn't say.
But Rep. Mark Meadows, R-North Carolina, a member of the House Oversight Committee, told reporters Comey was not being forthcoming enough.
"I can tell you that consistently the FBI has had legal counsel there to try to discourage the answering of certain questions that might be good for the American people to know and, yet, oftentimes they will suggest that it’s part of an ongoing investigation and discourage the witnesses from testifying," Meadows said.
But the top Democrat on the Oversight Committee, Rep. Elijah Cummings, D-Maryland, said that the hearing was a waste of time taxpayer money.
"Basically what we’ve been hearing is what we’ve been hearing over and over," Cummings said.
A transcript of Comey's testimony should be released Tuesday. House Republicans also plan to question former Attorney General Loretta Lynch this week, according to congressional aides.
Comey, who has been highly critical of Trump since his firing last year and spoken repeatedly to other congressional committees and news outlets about his experience, reached an agreement with Republicans to appear behind closed doors, provided they release a transcript of the hearing within 24 hours and allow him to speak publicly about the session after meeting with lawmakers. He had initially mounted a legal challenge to the subpoena.