Former FBI Director James Comey defended the Department of Justice's handling of the Russia investigation under his watch, as well as former Special Counsel Robert Mueller, recalling in an interview on Tuesday that he had told his staff that they didn't want to "smear innocent people" in the probe.

Appearing on MSNBC ahead of Mueller's expected testimony on Capitol Hill on Wednesday, Comey insisted that he and everyone at the DOJ "should have been fired" if they didn't pursue an investigation in Russia's meddling in the 2016 election and whether there was an "American connection" in its efforts.

He expressed hope that House Democrats would "attack" Attorney General William Barr for his handling of the release of the Mueller report and how he has "slimed the FBI," but stressed that the lawmakers' questions should be more focused on the content of the report.

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"This is a chance for the American people to learn what he found," Comey told MSNBC host Nicolle Wallace. "It's too bad that having published a 450-page report, that didn't get the job done, but it didn't. Folks don't know what he found. And you can ask him in a simple and straightforward way and get those details in front of the American people."

Comey later called his firing by President Trump, something he never expected. He also doubled down on his conviction that the launch of the Russia probe was justified, since the DOJ "didn't know what the facts were" at the time.

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"I asked the staff at the FBI, 'Do it well, do it discreetly, because we don't want to smear innocent people, especially in the middle of a political election year,'" Comey said, "'but we don't want to let bad guys know that we're onto them if there's something to this.' That's work we had to do."

He added: "I'm proud of the fact that we opened that investigation. I'm proud of the way we did it and I'm proud of the way Director Mueller and his team continued it."