"I do not understand: why he (Ullrich) didn't confess how it really was, like the others did in the Telekom team? Everyone doped," Hont told German daily newspaper Süddeutsche Zeitung. "In my next book, there will be a lot of information on Ullrich."
In d'Hont's first book - "Memories of a Soigneur" - which was published last spring, the Belgian revealed the Telekom team - which dominated the Tour de France in 1996 and 1997 - had extensively used banned blood-booster erythropoietin (EPO).
Former Telekom riders Bjarne Riis, in 1996, and Ullrich, 1997, won the Tour de France, but while Riis admitted using EPO during the period, the German has kept silent.
"Before the publication of my first book, Ullrich's adviser Rudy Pevenage begged me not to say anything, because they wanted to say what happened in their own time. "I held my promise, they didn't."
After the publication of his first book, a string of former Telekom cyclists including Riis and Erik Zabel admitted to using EPO, but Ullrich has stayed silent on the matter since retiring in February 2007.