Crucial documents, including letters from British soldiers alerting the War Office to the Holocaust, may have been destroyed in the chaos at the end of hostilities.

These records are believed to have included coded messages from Sergeant-Major Charles Coward, the head of the British prisoner of war camp at Auschwitz about what he witnessed there. These letters home to his wife included details to be passed on to "William of Orange", an agreed code for the War Office. The letters have never been found and experts believe they were almost certainly destroyed after being deemed of little importance.

In fact, almost no documentary trace remains of the work of MI9, the section of British military intelligence which communicated with European resistance movements and prisoners of war such as Coward.

The National Archives, which has been helping the JC in its hunt for documents about PoW camp E715 at Auschwitz, holds almost nothing from MI9 beyond a history of the section, written for internal consumption, and hundreds of questionnaires filled out by prisoners on release into British hands.

The first 200 British prisoners were taken to Auschwitz in September 1943 to work at the IG Farben chemical plant. By the winter of that year there were around 1,400 PoWs in the camp, working alongside Jewish prisoners. The British camp, although separate and protected by the Geneva Convention, was within sight of the Buna-Monowicz camp and so British soldiers witnessed the treatment meted out there and were told about the gas chambers and the ovens.

Roger Ryan, a researcher and Church of England vicar, who has made the study of E715 Auschwitz his life's work, said: "It will be a tragedy if some MI9 documents are lost to us.

"But we have to understand that during the chaos of the end of the war much was destroyed that would now help researchers to piece together a fuller picture of the Holocaust. At the time, many people were unaware of the significance of the documents they held in their hands."