Adolf Eichmann, the bureaucratic mastermind of the Holocaust, regretted that he failed to exterminate all of Europe's Jews, saying "there was more we could have done", recordings have revealed.

Eichmann showed only disappointment that some survived, according to newly declassified files. Looking back on his role in organising the systematic slaughter of Jews, gipsies and other groups, he says: "We didn't do our work correctly."

During the war Eichmann had served as "transportation administrator" for the Final Solution, organising the mammoth task of sending Jews to various death camps.

Eichmann boasted he "was no ordinary recipient of orders" and that he "was part of the thinking process; an idealist".

it contradicts Eichmann's defence during his 1961 Jerusalem trial for crimes against humanity that he was following orders and was in effect only a small cog in the Nazi machine. Eichmann was found guilty and hanged in 1962