Thomas Newsome, 36, was deployed overseas until April 17, when he is alleged to have made a "damaging disclosure of information relating to defence and which was in his possession by virtue of his position".

He was arrested and detained on 18 April following an investigation by the Metropolitan Police's Counter Terrorism Command.

Newsome was charged on Friday with offences contrary to section 2 and section 8 of the Official Secrets Act 1989.

He is also charged with failing to take care of documents or "to prevent the unauthorised disclosure of those documents as a person in his position may reasonably be expected to take" on 18 April.

Newsome appeared at Westminster Magistrates Court on Saturday, speaking only to confirm his name and date of birth.

His address - usually stated by defendants - was withheld on national security grounds, as were the names of his lawyers.

He is alleged to have shared a 10-page document with two senior officers who had clearance to view it and one civilian who did not - including by taking photographs of the document and sending them by social media.

Leak would pose a "real and immediate threat to British citizens outside the UK"

Prosecutor Brigid Fitzpatrick said the document - which Newsome allegedly had both digital and hard copies of - contained "highly sensitive military information".

If leaked, it would pose a "real and immediate threat to the lives of British citizens outside the UK" and "facilitate the targeting of personnel", Ms Fitzpatrick said.

Newsome is also accused of possessing separate secret information on a USB stick.

District Judge Michael Snow rejected a bail application and said Newsome would next appear at the court on 28 April.

A Ministry of Defence spokesman said: "We can confirm the arrest of a serving member of the armed forces.

"This matter is the subject of an ongoing investigation, therefore it would be inappropriate to comment further."