Defence Secretary Ben Wallace has said it would be an understatement to say he was angered by a data breach involving the email addresses of dozens of Afghan interpreters who worked for UK forces.
More than 250 people seeking relocation to the UK - many of whom are in hiding - were mistakenly copied into an email.
Mr Wallace has apologised to them, and launched an investigation. One person has been suspended, he said.
The MoD has also referred itself to the Information Commissioner's Office.
Speaking in the Commons, Mr Wallace said: "I apologise to those Afghans affected by this data breach and with Home (the Home Office) we are now working with them to provide security advice.
"It is an unacceptable level of service that has let down the thousands of members of the armed forces and veterans.
"On behalf of the Ministry of Defence, I apologise."
He added that armed forces minister James Heappey was in the region speaking to neighbouring states to see what more could be done.
The email was sent to interpreters who remain in Afghanistan or have been able to get to other countries.
Their email addresses could be seen by all recipients, showing people's names and some associated profile pictures.
The Information Commissioner (ICO), which has the power to issue enforcement notices and fines in the most serious cases, is already making enquiries with the MoD.
A spokesperson for the watchdog said people rightly expected their personal information to be handled securely especially where its loss could have devastating consequences, including possible threat to life.
Conservative MP Tobias Ellwood, who chairs the defence select committee, warned that the Taliban had not changed.
"We must get these interpreters out or they'll be hunted and killed," he told MPs, and suggested using "clandestine means" to get them to safety, if usual methods were unavailable.
"All means will be explored," Mr Wallace replied.
The email was sent by the team in charge of the UK's Afghan Relocations and Assistance Policy (Arap), which has been in contact with them since the Taliban took control of the country last month.
The team told the interpreters it was doing everything it could to help relocate them.
It also said they should not put themselves or their families at risk if it was not safe for them to leave their current location.
But one interpreter who received the email realised that more than 250 Afghans who worked with British forces had been copied into the email.
"This mistake could cost the life of interpreters, especially for those who are still in Afghanistan," they told the BBC.
"Some of the interpreters didn't notice the mistake and they replied to all the emails already and they explained their situation which is very dangerous. The email contains their profile pictures and contact details."
The MoD then sent another email 30 minutes later with the title "Urgent - Arap case contact" asking the recipients to delete the previous email and warning "your email address may have been compromised".
It recommended the interpreters change their email addresses.
Mr Wallace said the Ministry of Defence believed there were 900 "credible cases" for Arap resettlement still in Afghanistan beyond the 311 the government is currently speaking to.
Labour shadow defence secretary John Healey welcomed the defence secretary's apology but told the Commons that action now mattered most.
He told MPs: "These Afghan interpreters worked alongside our British forces and the government rightly pledged to protect them. Ministers must make good on those promises now."
'Just when you think it can't get worse...'
Ahmad, not his real name, is one of the 250 or so whose names were mistakenly shared by the MoD. In 2011, he was shot by the Taliban while working as an interpreter with British troops in Helmand.
He's currently in hiding in Afghanistan, living apart from his wife and baby daughter for their own safety.
He told the BBC he was really shocked and disappointed when he spotted the MoD's mistake.
"Just when you think it can't get worse than this, along comes the Arap team and does something that proves you wrong. I didn't really expect this from them," he said.
"I'm 100% sure that it will have a negative impact on our safety because you know that we are already displaced from our home town.
"Now we have to change our locations again and we have to change our email addresses."
Ahmad added that he now doubted whether he would ever get to safety in the UK.
"I'm not very optimistic, because when I see their carelessness and their neglect, I don't think we're going to be in the UK in the near future."
But he said he was clinging to hope that the UK would "finally do the right thing".
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