US President Donald Trump took to Twitter to defend his mental fitness for office saying he is "like, really smart" and a "very stable genius". The internet immediately erupted into peels of giggles over the president's "ridiculous" defense, unleashing a torrent of merciless mocking, jokes and jeers.

Trump's remarks came in response to serious questions raised over his mental health and capacity to carry out his presidential duties in Michael Wolff's new book, Fire and Fury: Inside the Trump White House.

The recently released tell-all has dominated headlines with its sensational anecdotes and claims that paint an unflattering, dysfunctional portrait of Trump's campaign, his closest aides and the first few months of his presidency.

"Now that Russian collusion, after one year of intense study, has proven to be a total hoax on the American public, the Democrats and their lapdogs, the Fake News Mainstream Media, are taking out the old Ronald Reagan playbook and screaming mental stability and intelligence," Trump tweeted.

"Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart. Crooked Hillary Clinton also played these cards very hard and, as everyone knows, went down in flames.

"I went from VERY successful businessman, to top TV Star to President of the United States (on my first try). I think that would qualify as not smart, but genius....and a very stable genius at that!"

The internet, however, was all but convinced by Trump's assertion and proceeded to mercilessly mock the president for it.

"This is the funniest thing I've ever read in my entire life," one Twitter user wrote.

Congressman Dan Kildee tweeted, "Trump saying he's a 'very stable genius' is like Nixon saying 'I'm not a crook.'"

"The tweet confirms what the book says about Sweet Potato Hitler," comedian Chris Titus added. "What is the quote? 'Better to not talk, people may think you're stupid, but it's better than opening your mouth and proving you are'."

"When I grow up I want to be a very stable genius," one person joked.

donald trump
Trump responded to questions about his mental capacity saying he's "a very stable genius" and Twitter couldn't stop laughing REUTERS/Carlos Barria