In a new book, Steve Bannon, the former White House chief strategist, calls a meeting of Trump campaign officials with a Russian lawyer in Trump Tower during the presidential campaign "treasonous" and "unpatriotic."
The book, "Fire and Fury: Inside the Trump White House," soon to be published by Henry Holt, was written by Michael Wolff, a columnist and an author who has written several books, including a biography of Rupert Murdoch. In it, Bannon rips into Donald Trump Jr.; White House senior adviser Jared Kushner; and then-campaign chairman Paul Manafort for taking a June 2016 meeting with a group of Russians who promised dirt on Hillary Clinton, the Democratic nominee.
"The three senior guys in the campaign thought it was a good idea to meet with a foreign government inside Trump Tower in the conference room on the 25th floor with no lawyers," Bannon said, according to a copy of the book obtained by NBC News.
"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,” he added.
Related: Trump hits back at Bannon, says he 'lost his mind'
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Bannon also said he believed that the Russians were taken after the meeting to meet Trump, something the president has denied happened.
"The chance that Don Jr. did not walk these jumos up to his father’s office on the twenty-sixth floor is zero," Bannon says in the book.
Russian lawyer Natalia Veselnitskaya told NBC News that she and her colleagues at the Trump Tower meeting did not meet or see then-candidate Trump. "Absolutely not true," the Russian lawyer told NBC's Natasha Lededeva.
Trump issued a scathing statement attacking his former adviser, saying Bannon had "lost his mind."
"Steve Bannon has nothing to do with me or my Presidency. When he was fired, he not only lost his job, he lost his mind," Trump said.
"Steve had very little to do with our historic victory, which was delivered by the forgotten men and women of this country. Yet Steve had everything to do with the loss of a Senate seat in Alabama held for more than thirty years by Republicans. Steve doesn't represent my base — he's only in it for himself," the president added.
The Guardian was the first to report on Bannon's remarks in the book.
NBC News has not confirmed much of the book. Wolff has been accused in the past of suspect reporting, most notably in his 1998 book "Burn Rate." In its review, the defunct media review Brill's Content cited 13 people depicted in the book as saying that Wolff invented or changed quotations and that they couldn't recall his taking any notes or recording their interviews.
Bannon left the White House in August after a shaky tenure in the first seven months of Trump's presidency.
Trump Jr., Manafort and Kushner met with Russian lawyer Veselnitskaya after Rob Goldston, a music publicist with ties to Russia who is close with the Trumps, told Trump Jr. last year in an email that Veselnitskaya had "information that would incriminate Hillary and her dealings with Russia and would be very useful to your father."
Trump Jr. then wrote "I love it" about the prospect of getting his hands on the material, according to copies of emails that he later made public.
Bannon, in the book, also anticipated that Robert Mueller's Russia probe will zero in on money laundering.
"You realize where this is going," Bannon says. "This is all about money laundering. Mueller chose Weissmann first and he is a money-laundering guy," referring to Andrew Weissmann, a senior prosecutor on Mueller's team. "Their path to f---ing Trump goes right through Paul Manafort, Don Jr. and Jared Kushner. It’s as plain as a hair on your face."
"They’re going to crack Don Junior like an egg on national TV," Bannon says in the book.