The grandfather of the new head of British intelligence - MI6, was a Nazi spy, known as the Butcher, DPA reported, citing information from the British newspaper "Daily Mail", quoted by BTA.
Blaise Metreveli was announced as the future head of the secret intelligence service earlier this month. She will be the first female Xi in the service's 116-year history.
Several newspapers reported today that her grandfather Konstantin Dobrovolsky had deserted from the Soviet Red Army to become a chief informant for the Nazis in Chernigov, Ukraine.
However, the UK Foreign Office, speaking on behalf of MI6, said Metreveli "neither knew nor met her paternal grandfather".
A spokesman added: "Blaise's family background is one of conflict and division and, as is the case for many people of Eastern European heritage, is only partly understood."
"It is this complex heritage that has contributed to her commitment to preventing conflict and protecting British society from contemporary threats from today's hostile states, as the next head of the MI6.“
The "Daily Mail" newspaper, which first revealed the family connection, said it had discovered hundreds of pages of documents in an archive in Freiburg, Germany, which showed that Dobrovolsky was known as the Butcher, as well as Agent No. 30 to Wehrmacht commanders.
He reportedly signed letters to his Nazi superiors with "Heil Hitler" and said that "personally" participated in the "extermination of the Jews".
Archival documents allege that Dobrovolsky robbed the bodies of Holocaust victims, participated in the murders of local Jews and laughed while watching the sexual assaults of female prisoners, the BBC reported.
The documents also say that Soviet leaders announced a reward of 50,000 rubles for the Nazi spy and called him "the greatest enemy of the Ukrainian people", DPA reported.
After the war, Dobrovolsky's wife, Barbara, and their two-month-old son fled to Britain, and in 1947 she married David Metreveli. Her son took his stepfather's name, but the "Daily Mail" reports that in some official documents his surname is still Dobrovolsky.
David became a radiologist and a veteran of the British Armed Forces, and his daughter Blaise Metreveli was born in 1977. She herself has not reacted to the latest information about her grandfather.
She joined MI6, which collects intelligence information abroad, in 1999 and is currently responsible for technology and innovation there. She will be the 18th head of the intelligence service when she takes over from Sir Richard Moore later this year.
On her appointment, she said she was "proud and honoured" to have been invited to lead British intelligence.
Blaise Metreveli is a graduate of Cambridge University, trained in rowing, and still does it regularly, and has held operational positions in the Middle East and Europe.