Data on nuclear submarines has been made available on the internet, after a technical error by Whitehall departments.

The secret information was clearly viewable by users who pasted parts of blacked out documents into word processing software, it was reported. The documents were online as part of Freedom of Information responses.

Details included how well the UK’s nuclear submarines could cope in a challenging incident, the BBC reported. A more “secure” version has now been published, it is understood. A spokesperson at the Ministry of Defence said it was “grateful” to the journalist at the Daily Star newspaper, who initially highlighted the problem.

"As soon as we were told about this, we took steps to ensure the document was removed from the public domain and replaced by a properly redacted version,” the spokesperson said.

Other departments have also reportedly published sensitive data online in similar document formats, which can be read in the same manner, but the nature of the contents is not known.