MI6 has cast distance between its new chief and her grandfather, who was this week revealed to have been a Nazi spy known as "the butcher".

Blaise Metreweli was announced as the incoming head of the Secret Intelligence Service earlier this month. She will be its first female "C" in its 116-year history.

With little known about her wider backstory, several newspapers reported on Friday that her grandfather was Constantine Dobrowolski, who defected from Soviet Russia's Red Army to become the Nazis' chief informant in Chernihiv, Ukraine.

However, the Foreign Office, which speaks on behalf of MI6, said Ms Metreweli "neither knew nor met her paternal grandfather".

A spokesperson added: "Blaise's ancestry is characterised by conflict and division and, as is the case for many with eastern European heritage, only partially understood.

"It is precisely this complex heritage which has contributed to her commitment to prevent conflict and protect the British public from modern threats from today's hostile states, as the next chief of MI6."

The Daily Mail, which first revealed the family link, reports that it found hundreds of pages of documents in an archive in Freiburg, Germany, which showed Mr Dobrowolski was known as "The Butcher" or "Agent No 30" by Wehrmacht commanders.

He reportedly signed off letters to his Nazi superiors with "Heil Hitler" and said he "personally" took part in "the extermination of the Jews".

The archive documents are said to suggest Mr Dobrowolski looted the bodies of Holocaust victims, was involved in the murdering of local Jews, and laughed while watching the sexual assault of female prisoners.

After the war, Mr Dobrowolski's wife, Barbara, and two-month-old son fled to Britain, and she married David Metreweli in 1947. Her son took his stepfather's name, but the Mail reports that on some official documents his surname was still Dobrowolski.

Mr Dobrowolski's son would go on to be a radiologist and UK armed forces veteran, and his daughter, Ms Metreweli, was born in 1977. She has not responded to the recent reports herself.

She joined MI6 - which gathers intelligence overseas - in 1999, and is currently responsible for technology and innovation there. She will be the agency's 18th head when she takes over later this year from Sir Richard Moore, a senior civil servant.

Upon her appointment, she said in a statement that she was "proud and honoured" to have been asked to lead.

Ms Metreweli is a Cambridge graduate, a rower and has previously had operational roles in the Middle East and Europe.