The Ministry of Defence is probing a major security breach after the identities of special forces soldiers were inadvertently published online.

The names and ranks of at least 20 elite soldiers and their links to elite units were listed in documents made publicly available on the internet by two publications associated with the British Army.

It is a major embarrassment for the MoD which said the “safety of our personnel is of paramount importance”.

The publications were updated recently, meaning some of the soldiers might have been engaged in live operations at the time. In the latest update 13 soldiers' links to the special forces were revealed.

The documents were intended for members of the armed forces but appear to have been widely published without basic safeguards like password protection.

Tom Tugendhat, the former security minister, who served in both Iraq and Afghanistan, said: "Thirty years ago terrorism coming from Northern Ireland made us all aware of operational security at home.

"It's clear that some of those lessons need to be learnt again."

British elite forces, the Special Air Service and the Special Boat Service and known by the motto Who Dares Wins, are the world’s most feared combat units and regularly deployed to hostile live operations for covert missions.

Their work is highly sensitive and secret meaning the MoD never comments on their activities or where they are deployed. ​Identities of serving and past personnel are closely guarded.

Soldiers, what they do and where, are shrouded in secrecy to prevent cover being blown and operations compromised but also to ensure the safety of elite soldiers and their families, who could otherwise become targets for terrorists or other malign actors. However, some elite troops have chosen to identify themselves after leaving the forces. In one case, one of the publications revealed the codename linking an individual to the special forces and then appeared to disclose that they were overseas on deployment.

The disclosure appears to be one of the biggest security blunders in recent times. In 2021, the identities of more than 100 special forces troops were disclosed accidentally in a document listing promotions within the army. However, this breach was confined to an email sent to civil servants and soldiers, rather than in documents made available to anyone who could find them online. 

The SAS was founded as a regiment in 1941 by David Stirling, a Scottish officer in the British Army, during the Second World War. It was originally conceived as a commando force operating behind enemy lines during the North African campaign against German and Italian forces.

The crack unit came to global attention almost exactly 43 years ago when the SAS stormed the Iranian Embassy on May 5 1980 in a bid to free hostages being held by terrorists.

Two years later soldiers were sent to the Falklands following the Argentine invasion and secretly dropped on the islands three weeks before the British task force arrived.

Today, the activities of UK special forces are highly classified but specialise in counterterrorism, hostage situations, special operations and reconnaissance.

The MoD said: "The safety of our personnel is of paramount importance, and we take data security extremely seriously. Where we become aware of any potential risk, we will always take immediate action."