The Ministry of Defence (MoD) said it had contacted those impacted by the breach, with officials offering advice on how to manage the potential risk posed by the data reveal.
According to reports, some of those whose information has been released are in hiding from the Taliban after the militants took control of the battle-torn country last month.
A spokeswoman for the department said: “An investigation has been launched into a data breach of information from the Afghan Relocations Assistance Policy team.
“We apologise to everyone impacted by this breach and are working hard to ensure it does not happen again.
“The Ministry of Defence takes its information and data handling responsibilities very seriously.”
A source confirmed Defence Secretary Ben Wallace had personally ordered the probe.
Officials said it would “inappropriate” to comment on the specifics of the case but, according to the BBC, the breach refers to an email.
The broadcaster reported that more than 250 people seeking relocation to the UK – many of whom are in hiding – were mistakenly copied into an email from the MoD asking for an update on their situation.
Some of the email addresses had photos attached, the report suggested.
Labour shadow defence secretary John Healey said: “We told these Afghans interpreters we would keep them safe, instead this breach has needlessly put lives at risk.
“The priority now is to urgently step up efforts to get these Afghans safely to the UK.
“This is the second major data breach from the MoD this year, after sensitive documents were discovered at a bus stop in Kent in June.
“Clearly, the Defence Secretary needs to get his house in order.”
The MoD said it would take all necessary steps under UK GDPR rules.Internet Explorer Channel Network