Sen. Angus King Angus KingShakespeare Theatre Company goes virtual for 'Will on the Hill...or Won't They?' On The Trail: How Nancy Pelosi could improbably become president Angus King: Ending election security briefings 'looks like a pre-cover-up' MORE (I-Maine) said on Thursday he agreed with recent comments from former White House chief strategist Stephen Bannon saying Donald Trump Jr. Don John Trump'Tiger King' star Joe Exotic requests pardon from Trump: 'Be my hero please' Zaid Jilani discusses Trump's move to cancel racial sensitivity training at federal agencies Trump International Hotel in Vancouver closes permanently MORE should have reached out to the FBI after the meeting with the Russian lawyer was proposed to him in 2016.

"I don't usually agree with Steve Bannon Stephen (Steve) Kevin BannonJuan Williams: Swamp creature at the White House Engineers say privately funded border wall is poorly constructed and set to fail: report Bannon and Maxwell cases display DOJ press strategy chutzpah MORE, but the idea that they should have immediately called the FBI is absolutely accurate," King told CNN's Chris Cuomo on "New Day."

"You clearly can say it was a serious mistake, a serious lack of judgment," he said, referring to the meeting.

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King's comments come after Bannon was quoted in author Michael Wolff's new book documenting the Trump White House, as saying Trump Jr.'s meeting with a Russian lawyer in exchange for negative information on then-Democratic candidate Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE was "treasonous."

“Even if you thought that this was not treasonous, or unpatriotic, or bad shit, and I happen to think it’s all of that, you should have called the FBI immediately," Bannon said in the book.

Reports last year revealed that Trump Jr., the president's son-in-law Jared Kushner Jared Corey KushnerAbraham Accords: New hope for peace in Middle East Tenants in Kushner building file lawsuit alleging dangerous living conditions Trump hosts Israel, UAE, Bahrain for historic signing MORE and Trump campaign chairman Paul Manafort Paul John ManafortBannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention Ukraine language in GOP platform underscores Trump tensions MORE had met with Russian lawyer Natalia Veselnitskaya in Trump Tower during the summer of 2016.

The meeting has since been the subject of congressional probes into alleged ties between the Trump campaign and Russia's election interference.

Trump Jr. responded to Bannon's comments on Wednesday in a tweet, ripping his endorsement of Roy Moore Roy Stewart MooreVulnerable Senate Democrat urges unity: 'Not about what side of the aisle we're on' Sessions hits back at Trump days ahead of Alabama Senate runoff Judge allows Roy Moore lawsuit over Sacha Baron Cohen prank to proceed MORE in the Alabama Senate race.

Thanks Steve. Keep up the great work. https://t.co/J9O8CUfJAD — Donald Trump Jr. (@DonaldJTrumpJr) January 3, 2018

The president also issued a statement slamming his former chief strategist.

“Steve Bannon has nothing to do with me or my presidency,” Trump said. “When he was fired, he not only lost his job, he lost his mind.”