Trump battled back in a series of posts on Twitter.
"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!" Tweeted the President.
Trump said Democratic critics and the U.S. news media were bringing up the "old Ronald Reagan playbook and screaming mental stability and intelligence" since they have not been able to bring him down in other ways.
Reagan, a Republican who was the U.S. president from 1981-1989, was often accused by his enemies of being too old to run the country. He used to joke about the ageist insults against him however, saying that he wouldn't take advantage of his some-50-year-old opponents' "youth and inexperience."
"Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart," said Trump, a former reality TV star and developer.
Trump, 71, sent the tweets from the presidential retreat at Camp David, Maryland, where he discussed a legislative agenda for the year with Republican congressional leaders and many Cabinet secretaries.
Wolff's book, "Fire and Fury - Inside the Trump White House," portrays Trump as unfocused, unprepared and petty while presiding over a chaotic White House.
Trump, answering questions from reporters at Camp David after the meeting, called Wolff a "fraud" and said the book is "a complete work of fiction."
"I think it's a disgrace," he said.
Indeed Wolff's work cannot be entirely, if at all, taken seriously. Despite the author's dubious past and previous works, in this new book he even says that some of the stories he heard could be outright lies, while others outright contradict each other.
Trump said he never granted Wolff an interview for the book and blamed former adviser Steve Bannon, who he called "Sloppy Steve," for granting Wolff access at the White House. Wolff claimed he spoke to Trump but that the president may not have known he was being interviewed.
Several details in Wolff's account already have been revealed to be highly unlikely, as Washington insiders have been quick to point out.