An apology has been issued and investigation launched after classified government documents were found sodden at a bus stop in Kent.

It is understood the sensitive defence papers contained details about destroyer HMS Defender and the likely Russian reaction to the ship's voyage through Ukrainian waters off the Crimea coast last week.

Another paper weighed up plans for a possible "UK military presence in Afghanistan" after the US-led NATO operation there ends.

The damp papers were found by a member of a public, although the exact location in the county has not been revealed.

They were handed to the BBC.

The Ministry of Defence has launched an investigation into how the papers were left behind by a member of staff, who self reported the error as soon as they realised the documents were missing.

Today, more questions were put to the government body about the loss of the secret documents during a session at the House of Commons.

"While the investigation is conducted, the individual's access to sensitive materials has been suspended..."

The topic was raised by John Healey, Labour MP for Wentworth and Dearne.

Jeremy Quin MP, Minister of State for Ministry of Defence, said: "The Ministry of Defence has launched a full investigation. The papers have now been recovered from the BBC and are being assesses as I speak to check all documents missing have been recovered and what mitigating actions might be necessary.

"The investigation will look at the actions of the individuals, including the printing of the papers through to the management of the reported incident and the underlying processes for printing and carrying papers in defence.

"The investigation is expected to be completed shortly. While the investigation is conducted, the individual's access to sensitive materials has been suspended."

Mr Healey said it was not the first time sensitive documents had been leaked and said the department needs to get a grip to ensure it doesn't happen again.

"The investigation is expected to be completed shortly..."

He also asked whether the military police were involved, and if espionage was being considered.

Mr Quin said they take the loss of all data and documents seriously, and said the military police were involved.

In terms of espionage, he said it was a matter for the investigation but repeated that the individual did self report when they realised the documents had been mislaid.

HMS Defender, a type 45 destroyer, is part of the UK Carrier Strike Group and is currently carrying out missions in the Black Sea, according to the Royal Navy's website.

It was involved in an altercation with Russian naval vessels last week over its journey through territorial waters.

On Wednesday, more than 20 Russian aircraft and two coastguard ships shadowed the warship.

Warning shots were reportedly fired at the destroyer.

According to the BBC's reports, three potential Russian responses were outlined in the found papers, from "safe and professional" to "neither safe nor professional".

An alternative route was also considered, which would have meant HMS Defender avoided the contested waters.

Most of the papers are allegedly marked "official sensitive" – a relatively low level of classification.

But the BBC reports that one document addressed to the defence secretary Ben Wallace’s private secretary was labelled “Secret UK Eyes Only”.

It apparently outlines highly sensitive recommendations related to the UK's military presence in Afghanistan, following the conclusion of Nato’s current operation.

The broadcaster says it decided not to report certain details which could endanger the security of British and other personnel.

During today's session in the House of Commons, it was questioned whether any official secrets legislation had been broken when the found papers were not handed to the police, rather than the BBC, and in turn if the BBC had broken any rules by not handing them straight to the Ministry of Defence.

Mr Quin said when documents of this nature are found it is preferential for them to be handed to the police, and said he recognises that the BBC have a job to do.

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