House Intelligence Chairman Adam Schiff Adam Bennett SchiffSchiff to subpoena top DHS official, alleges whistleblower deposition is being stonewalled Schiff claims DHS is blocking whistleblower's access to records before testimony GOP lawmakers distance themselves from Trump comments on transfer of power MORE (D-Calif.) defended the FBI’s investigation into President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE's campaign on Sunday, adding that the errors found by the Department of Justice inspector general’s (IG) report were not “apparent” two years ago.

The chairman argued on "Fox News Sunday" that while the FBI made "serious" mistakes relating to surveillance of Trump campaign aides under the Foreign Intelligence Surveillance Act (FISA), the investigation was still warranted.

Schiff added that he was “unaware of” the mistakes uncovered by Inspector General Michael Horowitz in his report released last week.

“I’m certainly willing to admit the inspector general found serious abuses of FISA that I was unaware of,” he said to host Chris Wallace Christopher (Chris) WallaceTrump, Biden will not shake hands at first debate due to COVID-19 Will Chis Wallace's debate topics favor Biden over Trump? House to vote on resolution affirming peaceful transition of power MORE. “Had I known of them, Chris, yes I would have called out the FBI at the same time. “

TODAY: Adam Schiff defends how the FISA investigation was conducted because the errors the IG found were not "apparent" two years ago. #FNS #FoxNews pic.twitter.com/4ojC14VGzo — FoxNewsSunday (@FoxNewsSunday) December 15, 2019

Schiff maintained that the FBI would have been “negligent” not to launch an investigation into the Trump campaign’s alleged ties to Russia, adding that the bureau should adopt the inspector general’s recommendations.

“The most significant things I think are that corrective steps will be taken in terms of the FISA process and that the IG debunked the claims of the president, by Mr. Nunes and others of this deep state conspiracy,” Schiff added, referring to Rep. Devin Nunes Devin Gerald NunesOvernight Defense: Stopgap spending measure awaits Senate vote | Trump nominates former Nunes aide for intelligence community watchdog | Trump extends ban on racial discrimination training to contractors, military Trump nominates former Nunes aide to serve as intel community inspector general Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election MORE (Calif.), the ranking Republican on the House Intelligence Committee.

The long-awaited Horowitz report released last week concluded the FBI did not act out of political motivation when opening the investigation. It did find 17 “significant inaccuracies and omissions” made by the bureau during its probe.