The newspaper says Gert Sudholt is a right-wing extremist who has been jailed for publishing revisionist history.
Sudholt, whose stepfather was deputy to Otto Dietrich, the Nazi press chief, has been prosecuted at least three times for printing far-right material, the newspaper said. He was jailed for six months in 1993.
Sudholt also runs the Society for Free Communication, which offers former Nazi Party members and their families a platform for their opinions.
The Daily Telegraph says the claims in "Himmler's Secret War," by Martin Allen, have been debunked by an independent forensic analyst working on behalf of the newspaper.
The analysis showed that at least four of the documents used to substantiate them were forgeries smuggled into the National Archives. Almost all historians accept that Himmler, the head of the SS, committed suicide soon after being captured by British soldiers in May 1945.