In an interview from his cell in Josefstadt Prison, in Vienna, the 67-year-old author of Hitler’s War, said: “Given the ruthless efficiency of the Germans, if there was an extermination programme to kill all the Jews, how come so many survived?”

Irving was jailed last week for three years for Holocaust denial and is appealing against that sentence. The maximum is ten years and the state prosecutor has asked the appeals court to increase the term. The Prosecutor’s Office made no comments yesterday on Irving’s latest outburst.

In his interview Irving said that he now accepted, on the basis of figures quoted in the personal papers of Adolf Eichmann, a key architect of the Holocaust, that the Nazis did murder millions of Jew”. He added, however, that Hitler’s involvement had “a big question mark behind it”.