In his first public reaction since the release of Trierweiler's memoir, Merci Pour Ce Moment (Thank You For This Moment), Hollande denied her claims that he dismissively called the poor les sans-dents (the toothless ones).
"I will never accept to have an entire life's commitment, everything that founded my political life, cast into doubt," Hollande said while attending the NATO summit in Wales.
Trierweiler's new book chronicles her time in the Elysee Palace as the partner to French President Franois Hollande.
"He presented himself as a man who disliked the rich," Trierweiler wrote, according to France24. "In reality, the president doesn't like the poor. In private, this man the left-winger calls them 'the toothless' and is so pleased at how funny he is."
Hollande and Trierweiler split earlier this year, after the tabloid magazine Closer published images of a man purported to be Hollande arriving at the apartment of actress Julie Gayet on a scooter.
Hollande's private life became very public and both split thereafter.
This week, as Trierweiler's memoirs hit the headlines, Hollande was attending a NATO summit in Wales. On Friday, the president defended himself against his former partner's accusations.
Hollande said he was completely committed to "the weakest, the most humble, the poorest," and called his work for them his "raison d'etre" and that he would "never accept ... that the commitment of a lifetime may be put into question."
In an interview with French radio, Segolene Royal Hollande's former partner who is also a politician and who recently joined his cabinet rejected Trierweiler's assertion as "total nonsense".
His popularity is currently at rock bottom: Bloomberg reported that Hollande's approval ratings are "back below 20 percent, near France's historical low for a president", says thestar.com.
Other revelations in the book include that when Hollande's relationship with Gayet hit the headlines, Trierweiler took a large dose of sleeping pills.
"I want to sleep," the book says. "I don't want to go through the hours that'll follow."
Tranquilizers feature in another scene. The Daily Telegraph cites a passage in which Trierweiler wrote that she was kept drugged to prevent her from attending an event with Hollande.
"Every time I try and put a foot out of the bed, I collapse I only understood why later. The doses of tranquilizers were over-multiplied to stop me going to Tulle," Trierweiler wrote, according to the paper.
Bookstores have reported "brisk" sales of the book, which is at the top of Amazon France's bestsellers.