Officials are assessing whether any sensitive defence documents are still missing following the discovery of a cache of classified material at a bus stop, MPs have been told.
Defence minister Jeremy Quin said a full investigation was under way after the papers were handed to the BBC by a member of the public who found them last week in Kent.
Responding to an urgent question in the House of Commons, Mr Quin said the leak appeared to be the result of a “mistake” by one individual who “self-reported” the loss to the Ministry of Defence (MoD).
The papers included documents relating the likely reaction of the Russians to the passage of the Royal Navy destroyer HMS Defender through waters off the coast of Crimea and to the UK military presence in Afghanistan.
Mr Quin said they included one paper that was classified “Secret – UK eyes only”.
“The papers have now been recovered from the BBC and are being assessed as I speak to check that all documents missing have been recovered and what mitigation actions might be necessary,” he said.
“The investigation will look at the actions of individuals, including the printing of the papers through to the management of the reported incident and at the underlying processes for printing and carriage of papers in defence.”
He said he hoped the investigation could be completed in “as little as a week” and that the official concerned had had their access to sensitive material suspended.
Shadow defence secretary John Healey, who secured the urgent question, said the loss of the material was “certainly embarrassing for ministers, but it is deeply worrying for those concerned with our national security”.
A number of MPs, including Tory backbenchers James Sunderland and Bill Wiggin and Labour’s Chris Bryant, suggested the official concerned should be required to “walk the plank” if they were found to have acted negligently.
Mr Quin said that he did not want to pre-empt the result of the MoD investigation.
But he told the House: “This is a mistake, it appears. I don’t want to prejudge the investigation, but it appears it’s a mistake made by an individual. It’s important that one gets on top of that mistake and what can be learned.”
Mr Quin declined calls by some Conservatives to condemn the BBC for broadcasting some details of the papers’ contents.
“Although I would have preferred naturally the BBC to have handed them over immediately and not made reference to them, they have a job to do and I also recognise that they have behaved responsibly and they have handed the documents back into the department,” he said.