The mother of new Labour Party leader Ed Miliband is a long-standing supporter of left-wing pro-Palestinian organisations.
Marion Kozak, 75, who maintained a low profile as Ed defeated his brother David to become leader of the Opposition, is a signatory of the founding statements of both Jews for Justice for Palestinians (JfJfP) and Independent Jewish Voices (IJV).
Her sons both described themselves as "critical friends" of Israel during a leadership hustings in June. Ms Kozak is a long-standing human rights campaigner and was an early CND activist.
She was born in Poland and fled Nazi persecution as a child during the Holocaust. She settled in Britain and married influential Marxist intellectual Ralph Miliband.
Richard Kuper, JfJfP co-founder, said: "Marion is a long-standing supporter, but she keeps a low profile and is a very private woman. She signed up fairly early on with our campaign."
He said people should not be shocked by her support for the group. "It's not a surprise. She's a very principled woman. I don't think anyone should bat an eyelid."
JFJFP's founding statement outlines its opposition to "Israeli policies that undermine the livelihoods, human, civil and political rights of the Palestinian people" and pledges to ensure "that Jewish opinions critical of Israeli policy are heard in Britain".
Independent Jewish Voices' declaration claims that British Jewish organisations do not reflect the Jewish community as a whole.
One member of IJV's steering group said Ms Kozak was a supporter, but not a leading member of the campaign.