Democratic Reps. Elijah Cummings of Maryland and Jerrold Nadler of NY said the report shows the FBI helped Trump get elected and that the agency should not have spoken publicly about the investigation into Hillary Clinton's email.
Horowitz's report also took issue with several FBI employees, whom he said "sent political messages - some of which related directly to the midyear investigation - that created the appearance of bias and thereby raised questions about the objectivity and thoroughness of the midyear investigation".
"Our judgment is that no reasonable prosecutor would bring such a case", Comey said after detailing the FBI's findings in its investigation of Clinton's use of personal email servers.
The FBI found no evidence to charge Clinton, and Comey announced - just two days before the election - that the case was closed.
Comey already has been criticized for waiting a month to act during the 2016 presidential election campaign after thousands of emails were discovered on Weiner's laptop that appeared to be relevant to the Clinton investigation.
Trump regularly claims McCabe had a conflict of interest in overseeing the FBI's investigation into Clinton, given that his wife received campaign donations from a Clinton ally. But it said that senior leaders' handling of the Clinton case cast a cloud over the bureau and did lasting damage to the FBI's reputation.
Trump was set to receive a briefing Thursday on the 500-page report, which the president is widely expected to use to launch fresh attacks against not only Clinton but also the law enforcement officials behind special counsel Robert Mueller's Russian Federation probe, which Trump has repeatedly referred to as a "witch hunt". If McCabe can produce evidence exonerating him from charges that he leaked to the press, that would mean Comey was the one "lacking candor" - Federal Bureau of Investigation speak for lying under oath. She did not formally recuse herself from the investigation after criticism arose over the encounter, but rather said she would accept the recommendations of career Justice Department staff and the FBI.
A long-serving law enforcement official, Mr Comey became a controversial figure in the 2016 election, drawing accusations from both Republicans and Democrats that his handling of an investigation into Mrs Clinton's emails influenced the campaign.
Comey's comments come in response to the public release of a report that is heavily critical of his decisions in the probe. He writes, "We draw the distinction in noting we have no evidence classified information was ever shared with an unauthorized party, i.e. notwithstanding the server setup, we have not seen classified information shared with a member of the media, an agent of a foreign power, a lover, etc".
"Although we did not find clear evidence that Secretary Clinton or her colleagues meant to violate laws governing the handling of classified information, there is evidence that they were extremely careless in their handling of very sensitive, highly classified information", Comey said at the news conference. Trump has repeatedly claimed that Comey's investigation into Clinton was "phony and dishonest", claims that have now been shot down by his own administration. "And nothing in the inspector general's report makes me think we did the wrong thing".
Napolitano emphasized that Special Counsel Robert Mueller fired Peter Strzok and Lisa Page when he learned about the relationship and the text messages. When they fixate on the latter, they risk becoming the former.