Cardinal Tarcisio Bertone, a deputy to Pope Benedict, said Pius XII is the victim of a "black legend," ANSA said Wednesday.
"He is falsely painted as indulgent with Nazism and insensitive to the fate of their victims," Bertone said.
ANSA said controversy over Pius XII's stance on Nazism have slowed efforts to canonize the pontiff.
Pius XII was pope from 1939 to 1958.
Critics say a firm, public stance from the pope could have changed the course of the war and stopped German leader Adolf Hitler earlier, ANSA said.
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