The 65 drawings were unveiled to the public during the launch of "Vincent van Gogh: The Lost Arles Sketchbook" at a press conference in Paris on Tuesday.
The book's author, Bogomila Welsh-Ovcharov, a renowned art historian and professor emeritus at the University of Toronto, did not include the view of the Van Gogh Museum -- widely accepted to be the world's authority on the artist -- in the new publication.
The Van Gogh Museum released a statement
Tuesday saying that their opinion was intentionally excluded from Welsh-Ovcharov's book and that it wasn't the first time they concluded that the drawings were fakes.
The sketchbook's anonymous owners approached the museum in 2008 and 2012 and were told they were imitations, Louis van Tilborgh, a senior researcher at the museum, told CNN.
In 2013, before the book went to print, the museum told Welsh-Ovcharov the same thing.
Van Tilborgh told CNN the drawings are counterfeits and that Welsh-Ovcharov failed to spot "iconic mistakes."
The sketches do not reflect Van Gogh's style or artistic development, which was undergoing a "great transformation" during 1888 to 1890, the time that they were supposedly drawn, he says.
"We see many typical mistakes," Van Tilborgh said. "The style is totally different ... it's just chaos. The person who made them is following the examples of Van Gogh in a superficial way and doesn't know what Van Gogh was aiming for."
A controversial paper trail
The museum also said that the paper used in the sketches is not of the type Van Gogh ever used. The artist used black and purple ink, the museum said -- these sketches featured brown ink.
Welsh-Ovcharov addresses this discrepancy in her book -- claiming the brown ink was originally black but appears brown due to discoloration.
But museum experts say that her theory is "impossible" as the brown ink has been tested and identified as sepia shellac -- a brown ink.
Van Tilborgh said that it would have been "marvellous" if the sketches were indeed real and that the museum would have "loved to accept it."
French publisher Le Seuil and Bogomila Welsh-Ovcharov were not immediately available for comment.