Donald Trump went on the offensive Saturday after days of damaging claims about the state of his mental health with an attack on his political opponents and a boast that his presidential victory was proof of his “very stable genius”.

In a series of Twitter posts, the 71-year-old president claimed the US Democrats and the media had focused on his intelligence and state of health because an investigation into alleged collusion between his campaign and the Russian state had been a “total hoax”.

Mr Trump has been stung by claims in a book by Michael Wolff and the author’s subsequent comments that everyone surrounding the president questioned his fitness for high office.

Mr Wolff’s book – Fire and Fury – was released early after threats by Mr Trump’s lawyers to halt publication, with the book painting a picture of a dysfunctional White House led by a thin-skinned and mercurial president, unwilling to take advice with little grasp of policy detail.

In one interview, Mr Wolff said that the president was like a child who had “less credibility than, perhaps, anyone who has ever walked on earth”.Mr Trump responded on Saturday accusing the Democrats and media of using the same tactic as Hillary Clinton to question his suitability for office.

He suggested they were using the “old Ronald Reagan playbook”, referring to the former two-term president who was diagnosed with Alzheimer’s disease five years after leaving office.

“Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart,” he wrote.

He cited his rise from “VERY” successful businessmen to television star hosting his own reality programme to becoming a president at the first attempt. “I think that would qualify as not smart, but genius…and a very stable genius at that!”The continued broadside on Saturday overshadowed a strategy meeting by Mr Trump and his top aides at the presidential retreat of Camp David as they charted their course for 2018.

Mr Trump is to have the first physical examination of his presidency next week, a fixture announced after he slurred part of his speech announcing that the US recognised Jerusalem as the capital of Israel.

Despite attempts to raise doubts about the author’s credibility, the controversy has seen the book shoot to the top of the bestseller charts. White House spokeswoman said earlier this week that the book includes “mistake after mistake after mistake”.The continued broadside on Saturday overshadowed a strategy meeting by Mr Trump and his top aides at the presidential retreat of Camp David as they charted their course for 2018.

Mr Trump is to have the first physical examination of his presidency next week, a fixture announced after he slurred part of his speech announcing that the US recognised Jerusalem as the capital of Israel.

Despite attempts to raise doubts about the author’s credibility, the controversy has seen the book shoot to the top of the bestseller charts. White House spokeswoman said earlier this week that the book includes “mistake after mistake after mistake”. The continued broadside on Saturday overshadowed a strategy meeting by Mr Trump and his top aides at the presidential retreat of Camp David as they charted their course for 2018.

Mr Trump is to have the first physical examination of his presidency next week, a fixture announced after he slurred part of his speech announcing that the US recognised Jerusalem as the capital of Israel.

Despite attempts to raise doubts about the author’s credibility, the controversy has seen the book shoot to the top of the bestseller charts. White House spokeswoman said earlier this week that the book includes “mistake after mistake after mistake”.