US Secretary of State Rex Tillerson stated that he has never doubted President Trump’s mental health after a new book claimed staff saw him as a child.

Author Michael Wolff said White House employees believed Mr Trump’s “mental powers were slipping”.

His book, Fire and Fury: Inside the Trump White House, went on sale early despite the president’s attempts to block its publication.

Trump stated that the book was “boring and untruthful” and Wolff a “total loser”.

Furthermore Trump stated that it was being pushed by the media and others to hurt him. He added in a tweet: “They should try winning an election. Sad!”

Michael Wolff is a total loser who made up stories in order to sell this really boring and untruthful book. He used Sloppy Steve Bannon, who cried when he got fired and begged for his job. Now Sloppy Steve has been dumped like a dog by almost everyone. Too bad! https://t.co/mEeUhk5ZV9

— Donald J. Trump (@realDonaldTrump) January 6, 2018