“Among the 1,600 folders of documents reported missing since 2005 are letters from Sir Winston Churchill to General Franco, the Spanish dictator; minutes of Harold Wilson’s meetings with the Queen; and documents from the courts of Henry VIII, Elizabeth I and Charles I.
Dozens of regimental diaries, medal records and squadron and battleship logbooks have also seemingly disappeared.
Some of the files, many of which contain the sole copies of historical documents, have not been seen since the early 1990s and fewer than a half have been recovered, according to a register of missing items released under freedom of information laws.
Historians have accused the National Archives, which is overseen by the Ministry of Justice, of “administrative laxness”.
Dr Andrew Roberts, a Second World War expert and scholar on the Royal family, said: “It should be a top priority of Government to ensure these files are tracked down as soon as possible because they are of the first importance.
“There is nothing more frustrating as a historian to call up papers from an archive and find that the reason you cannot have them is not because of a 50–year rule preventing disclosure, but because of bureaucratic negligence or incompetence.”
Dr Tristram Hunt MP, the historian and MP who sits on the all–party Parliamentary group on archives and history, said: “To have areas of the national memory erased like this is worrying.” He plans to table written questions to Lord McNally, the Justice Minister with responsibility for The National Archives, to ask about the documents.
“I’m hopeful it’s a temporary aberration,” he said. “These things do get lost and come back to life.
“History is an asset in this country. It’s a natural resource, like oil. We have a lot of it and we need to take care of it.”
An archives spokesman said the majority of the missing papers were thought to still be at its depository in Kew, Surrey.
She said that incidences of theft were rare and most of the missing files were believed to have been put on the wrong shelves by staff after being consulted by a reader.
Papers could become lost in transit while being borrowed by government departments, she added.
She said the missing files amounted to 0.01 per cent of the collection, and there is a continual programme to search for lost items.
Among the items lost for more than a year were the British plans for D–Day, including original correspondence between Gen Dwight Eisenhower and Field Marshal Bernard Montgomery.
The operations record book of 617 Squadron – the legendary Dambusters – was listed as “misplaced” for 18 months after being lent to a Labour–run government department.
Two bundles of documents from the war crimes trial of SS commander Fritz Knoechlein, who had 97 prisoners of war from the 2nd Battalion, Royal Norfolk Regiment mown down by machinegun in the Le Paradis massacre of May 1940, were mislaid by staff for nine months.
Among the oldest missing papers are exchequer rolls from the 1220s and a Papal Bull from Pope Clement V in 1309, encouraging the foundation of Ciscertian abbeys.”