The report – published Tuesday – said although Walther Sommerlath belonged to the NSDAP Nazi party, he appeared to have been an inactive member and had helped a Jewish businessman escape the Holocaust.
Swedish media reported in 2002 that Sommerlath had joined Germany's Nazi party in 1934 and took over Efim Wechsler's consumer goods company under unclear circumstances in 1939.
But in Tuesday's report, World War II expert Erik Norberg said documents indicate that just before the outbreak of World War II Sommerlath helped Wechsler escape Germany to South America, where he had offered him a coffee plantation and other assets in exchange for the company.
Norberg said the offer was "clearly an attractive one," because the exclusion of Jews from business life in Germany meant he could not take his assets with him.
However, other researchers have questioned the nobility of Sommerlath's actions, as he too gained from the deal.
'Suspicions of a whitewash'
The American Gathering of Holocaust Survivors and their Descendants on Tuesday dismissed the report's findings as "self-serving" and said they lacked credibility.
"The report was not an independent inquiry - it was commissioned by the queen with the participation of her cousin, a Brazilian lawyer. Such a probe can only raise suspicions of a whitewash," the organization said in a statement.
"What Queen Silvia has produced only raises further troubling questions," it added.
Silvia commissioned the report in May, in reaction to the Swedish "Kalla Fakta" ("Cold Facts") TV program that portrayed her and her father negatively, the Royal Court said at the time.
On Tuesday, she was quoted as telling local daily Goteborgsposten that she was surprised by the report's findings.
"All this has come as a complete surprise to me and my brothers," Silvia said. "Our father never told us anything about this time and us children never asked either."
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