In a point-by-point rebuttal of the museum's damning assessment of the sketchbook -- apparently from the artist's legendary stay in the French city of Arles -- the experts also questioned its "monopoly" on deciding what is and is not by Van Gogh.

The main expert behind the find, Canadian art historian Bogomila Welsh-Ovcharov, hit back at their questioning of its authenticity, while British scholar Ronald Pickvance said there was no chance the 65 drawings were forgeries.

"These are absolutely OK, from one to 65," he said. "End of song, end of story."

Welsh-Ovcharov had earlier accused the Van Gogh Museum of basing its verdict on photographs of drawings rather than properly examining 10 originals which she had brought to them.

Her book, "Vincent Van Gogh, the fog of Arles: the rediscovered sketchbook" detailing the find, is being published in six countries on Thursday despite the controversy.

Her French publishers Le Seuil said, "To put an end to this controversy, we are offering the Van Gogh Museum the possibility of jointly organising a public debate between experts.

"This will also be an opportunity to shed light on the conditions under which the Van Gogh Museum is claiming the de facto right to a monopoly of attribution," their statement added.

But the museum's senior researcher Dr Louis van Tilborgh told AFP Wednesday that even after reading the book "we would not be changing our opinion. We think the author of the drawings is not Van Gogh but someone imitating him."

"Someone has done their best to make out that that the drawings could be by Van Gogh. They have imitated his style and iconography. But in imitating him, errors have appeared," he added.

jpegMpeg4-1280x720"It is hard to say when these imitations were done, by whom and why," Dr van Tilborgh added.