The information came to light in the memoirs of former secretary of the Nobel Committee Geir Lundestad.
Lundestad revealed in his book that Korhonen accused Ahtisaari of poor morals and of doing peace mediation talks for personal financial gain.
Korhonen was a close collaborator of Urho Kekkonen in the Foreign Ministry and worked in the 1970s for a short time as Foreign Minister in Martti Miettunen's government.
He opposed Finland's membership in the EU in the 1990s and was the leading anti-European candidate for president in the 1994 race that saw Ahtisaari elected president.
