Fox Business Network's Dagen McDowell didn't hold back when reacting to former FBI director James Comey's appearance on "Fox News Sunday," calling his initial retention the Trump administration's "biggest mistake."

"I can tell you one thing, his breath must stink because he's been regurgitating garbage for years now," McDowell said while co-hosting "The Five" Monday. "He should have never been the FBI director ever. Biggest mistake in the Trump administration."

COMEY ADMITS ERROR IN DEFENSE OF FBI'S FISA PROCESS AFTER IG REPORT: 'I WAS WRONG'

Comey admitted to anchor Chris Wallace that the recently released Justice Department Inspector General’s report on the launch of the Russia investigation and the FBI's use of the surveillance process showed that he was "overconfident" when he defended his former agency's use of the Foreign Intelligence Surveillance Act (FISA).

Inspector General Michael Horowitz’s report and testimony before the Senate Judiciary Committee last week detailed concerns that included 17 “significant errors and omissions” by the FBI’s investigative team when applying for a FISA warrant to monitor former Trump campaign adviser Carter Page.

McDowell accused Comey of "gross incompetence," saying he hurt the country.

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"It damages the United States and it puts us at risk because these are not regular warrants. These are warrants that you get in front of a secret court," she said. "There are 50 facts that can only be explained by gross incompetence or bias."

"Jim Comey is either dense or he's pathological," McDowell added.

Co-host Jesse Watters agreed with McDowell.

"And lying to a judge, concealing evidence and forging information. Those aren't just sloppy mistakes," Watters said. "That's intentional bias, misconduct."

Fox News' Ronn Blitzer contributed to this report.