The Government has been accused of “lax” security after top secret documents were left at a bus stop. 

Senior sources within the US Department of Defence told The Telegraph “an FBI investigation would ensue” if a similar situation had played out in the US, in which a senior civil servant lost a 50-page secret dossier after removing it from a secure building. 

They said: “At the very least, the person in question would either be asked to resign, forced to take early retirement or be permanently stripped of his security clearance and redeployed to a role where no security clearance was required.”

It is understood that Angus Lapsley, who was director for defence, international security and south-east Europe at the Foreign Office from 2017 until 2019, was the person who lost the documents.

It is understood that while Mr Lapsley, who was set to be made ambassador to Nato, had his security clearance suspended and was removed from the Ministry of Defence after the breach, he remains in post at the Foreign, Commonwealth & Development Office.

A government source told The Telegraph that while Mr Lapsley’s security clearance was suspended, “it doesn’t mean it won’t be reinstated at a later date”. 

The US official cautioned that the “lack of discipline” displayed towards Mr Lapsley raised “serious questions about UK-US intelligence”.

“The way it has been handled does not instil confidence,” they said. “Why was he even taking such documents out of the building? Obviously, the British are more lax than we are.”

In June, it was revealed that a senior official had left a 50-page secret dossier at a bus stop in Kent. 

The documents, some of which were marked “Secret UK Eyes Only”, discussed the likely Russian reaction to HMS Defender’s passage through Ukrainian waters as part of the Carrier Strike Group’s maiden operational voyage. 

It is understood that Mr Lapsley, who also held a number of senior positions within the Civil Service, was being considered for an appointment as the UK’s ambassador to Nato at the time of the incident.

In 1986, Lord West left documents detailing large cuts to the Navy on a canal towpath, which resulted in the former First Sea Lord being court martialed. 

Days of taking papers home ‘are long gone’

Sir Iain Duncan Smith, the former Conservative leader, also questioned why Mr Lapsley had taken such sensitive documents home. 

“The message should go out very strongly that the days of taking papers home are long gone,” he said, adding that there was “no excuse” to do so when encrypted communications on secure computers were readily available. 

Sir Iain added: “It should be a significant offence to take papers home. It was a terrible security mess and he shouldn’t be carrying stuff like that home when it’s classified. I hope the Government is making a real point that anyone who takes papers home will find themselves being disciplined.” 

A Government spokesman said: “The UK Government takes the protection of its information extremely seriously. The investigation has independently confirmed the circumstances of the loss and the manner in which it occurred. 

“The investigation has confidence that all secret papers were recovered, there was no evidence of espionage and there has been no compromise of the documents by adversaries. 

“The individual concerned has been removed from sensitive work and has already had their security clearance suspended pending a full review.”