Former White House aide Steve Bannon "lost his mind" when "he was fired" from his job at the White House, US President Donald Trump has said in a fierce statement.

It came just hours after news broke that Bannon had made incendiary criticisms about a meeting between Trump's son Donald Trump Junior, his son-in-law Jared Kushner, Trump campaign chairman Paul Manafort and Russian lawyer Natalia Veselnitskaya at Trump Tower in New York.

Bannon reportedly called the 2016 meeting with the Russians "treasonous" and "unpatriotic".

Trump hit back on Wednesday, saying "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."

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"Steve was a staffer who worked for me after I had already won the nomination by defeating seventeen candidates, often described as the most talented field ever assembled in the Republican party.

"Now that he is on his own, Steve is learning that winning isn't as easy as I make it look. 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.

"Steve pretends to be at war with the media, which he calls the opposition party, yet he spent his time at the White House leaking false information to the media to make himself seem far more important than he was. It is the only thing he does well.

"Steve was rarely in a one-on-one meeting with me and only pretends to have had influence to fool a few people with no access and no clue, whom he helped write phony books," Trump's statement said.

Bannon's comments will be published next week in Fire and Fury: Inside the Trump White House by Michael Wolff, which promises to blow the lid on the chaos inside Donald Trump's administration.

The Trump Tower encounter was set up after an intermediary promised to share dirt on Trump's presidential rival, Hillary Clinton.

"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 after the meeting was exposed in The New York Times, according to the book.

"Even if you thought that this was not treasonous, or unpatriotic, or bad s**t, and I happen to think it's all of that, you should have called the FBI immediately."

Donald Trump Jr during an interview with Sean Hannity on Fox News. Photo / File
Donald Trump Jr during an interview with Sean Hannity on Fox News. Photo / File

Bannon suggested it would have been smarter to hold the meeting in New Hampshire, away from prying eyes, and with lawyers in attendance.

The incriminating information could then have been leaked to the press.

"Breitbart or something like that, or maybe some other more legitimate publication," Bannon said.

Ultimately, Trump's former top political adviser suggests the team lacked the necessary smarts to handle the situation.

"But that's the brain trust that they had," he said.

While Trump has continued to play down the significance of the investigations into whether his campaign colluded with the Russian government to sway the election in his favour, Bannon expressed shock at the White House's lack of concern.

"They're sitting on a beach trying to stop a Category Five," he said.

Bannon predicted Robert Mueller's probe would focus on money laundering as a way to get to the President.

President Donald Trump waves as he arrives to board Air Force One at Palm Beach International Airport on New Year's Day. Photo / AP
President Donald Trump waves as he arrives to board Air Force One at Palm Beach International Airport on New Year's Day. Photo / AP

"You realise where this is going," Bannon said, according to the book.

"This is all about money laundering. Mueller chose [senior prosecutor Andrew] Weissmann first and he is a money-laundering guy. 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 also suggested that the subpoena of Deutsche Bank accounts held by Trump and his family would be significant.

"It goes through Deutsche Bank and all the Kushner s**t. The Kushner s**t is greasy. They're going to go right through that. They're going to roll those two guys up and say 'play me or trade me'."

In June of 2016, music promoter Rob Goldston emailed Donald Jr to say that "the crown prosecutor of Russia" could provide to the Trump campaign "official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father".

Donald Jr replied: "If it's what you say, I love it."

After the Times broke the story, the President's son said the eventual meeting in Trump Tower with Ms Veselnitskaya amounted to nothing.

Bannon has returned to his role as executive chairman of right-wing news website Breitbart after he was booted from the White House.

However, he remains in regular contact with the President and is trying to lead an anti-establishment insurgency within the Republican Party.

Bannon had a famous rivalry with Trump's daughter Ivanka and her husband Jared Kushner, who are both more moderate politically.

The right-wing firebrand strenuously backed accused child molester Roy Moore in his race for a Senate seat in Alabama last month, which brought him into conflict with Ivanka, who said there was a "special place in hell for people who prey on children".

Bannon used that phrase against her during an Alabama rally, saying there was a "special place in hell" for Republicans who failed to back Moore.

The conservative judge was narrowly defeated in the final vote, with Democrat Doug Jones picking up the seat in what is a staunchly Republican state.

Wolff's book is based on more than 200 interviews with the President and his inner circle and promises to tell "the inside story of the most controversial presidency of our time".

The book will be released on Tuesday.