His father was arrested and held in Buchenwald, Auschwitz, and Dachau, but survived to reunite with Spiegel and his mother in Warendorf after the war.
Siegel was the nephew of Siegmund, a cattle and horse trader, and Marga Spiegel, both of whom survived the Holocaust with the help of farmers and their families.
On the 58th anniversary of the liberation of Auschwitz in 2003, Spiegel and Chancellor Gerhard Schröder signed an agreement that granted Germany's Jewish community the same legal status as the country's Christian religions, thereby tripling annual government funding of the Zentralrat der Juden to $3.8 million.
Spiegel was an outspoken critic of lawyers who took what he felt were overly large fees to represent Jews who had been slave laborers during World War II, saying "Earning money should not come before moralistic intentions."
He also criticized the national Holocaust Memorial in Berlin, stating at its dedication in 2005 that it failed to address the basic question, "Why were members of a civilized people in the heart of Europe capable of planning and carrying out mass murder?"