This is old hat first brought up by the Roman Catholic Church to demonize Jews many centuries ago. It was never proved but kept alive by succeeding Popes for purposes already stated. The author is not the instigator of the story nor could he produce proof for there wasn't any. Sadly there are still people within the Vatican who would like it to be true.
Ya'alon met with security chiefs to assess situation following developments at Gaza border (Haaretz)
from the article: MKs demand the author of blood libel book be prosecuted