In extracts of her tell-all memoir titled sarcastically, “Thank You for this Moment” (Merci pour le moment) Trierweiler claims that the Socialist president is not too fond of France’s poor people.
Hollande, who is already deeply unpopular among those on the left, apparently refers to the poor as the “sans-dents”, (the toothless ones).
Trierweiler writes: “He portrays himself as a man who doesn’t like the rich. But in reality, the president does not like poor people.
She continues: “Him, a man of the left says in private: “les sans-dents”, very proud of his humour.”
Trierweiler’s claims have provoked both anger and mockery in France, where the release of the book has dominated headlines.
The National Front were quick to react after hearing of Trierweiler's claims.
“Hollande despise the “sans dents”. This is probably the most interesting information in the book,” said a statement from the party.
Party leader Marine Le Pen said: “If he said this, then it would reveal a face of François Hollande that would definitely ruin his image among those who put their trust in him.”
UMP deputy Valerie Boyer described it as “an expression of cynicism and contempt that is not acceptable”.
The hashtag #sansdents topped the Twitter trends in France on Thursday and it prompted Twitter users to use their photo shop skills, by removing Hollande’s teeth from various photos.
Trierweiler's book finally hit the shelves on Thursday after being kept tightly under wraps. It was even printed in Germany to prevent any leaks.
It has already become the best-selling book on Amazon France, shooting to the website's number one spot in just one day and overtaking the hugely popular erotic novel "Fifty Shades Of Grey."
According to RTL radio the president’s entourage has denied using any such expression to describe poor people.
Hollande's partner before Trierweiler Ségolène Royal described the "toothless" claim as "nonsense and said Hollande should be judged on "his acts and on the evidence".
On Thursday Prime Minister Manuel Valls slammed the "excessive attacks" on the president.