Donald Trump has launched an attack on former chief strategist Steve Bannon, ahead of the release of an unflattering book.
The US President distanced himself and his administration from Mr Bannon in a particularly abrasive statement, 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," Mr Trump added, in a statement issued by the White House.
The President went on to accuse his former ally of "spending his time at the White House leaking false information to the media to make himself seem far more important than he really was".
He added: "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."
His statement comes after Mr Bannon was quoted in an excerpt from a new book as saying that a Trump Tower meeting between the President's son and a group of Russians, which he stressed was attended without lawyers, was "unpatriotic" and "treasonous".
The book – Fire And Fury: Inside The Trump White House, by Michael Wolff – also claims that Mr Trump never expected to win the 2016 presidential race, but believed his nomination would boost his brand and deliver "untold opportunities".
White House spokeswoman Sarah Sanders claimed the book was filled with "false and misleading accounts", and called Mr Bannon's accusation "ridiculous".
Mr Bannon, viewed by many as the architect of Mr Trump's campaign, left the White House in August after a string of disagreements with the President and his allies.
The strategist had contradicted Mr Trump's policy on North Korea in a media interview, had taken attention away from the President and was viewed by some as a symbol of the far right who could be bad for the former magnate's image.
Initially returning to his post as executive chairman of alt-right media outlet Breitbart News, Mr Bannon had pledged support for Mr Trump even after he left the White House, saying he was "going to war" for the President "on Capitol Hill, in the media and in corporate America".
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In Wolff's book, Mr Bannon also alleges that an investigation into Russian interference in the 2016 election will focus on money laundering.
In his statement, Mr Trump also referred to his own achievements, saying "Steve is learning that winning isn't as easy as I make it look".