Some 34 members of staff have been subject to disciplinary action since 2017, although the MoD has said the figure could be higher due to ongoing investigations.
The SNP which obtained the figures, said the scale of the leaks were “truly worrying” and called for a review of policies and procedures.
However, the MoD said the majority of the incidents in question were “minor breaches” of its social media policy.
The figures only include those incidents where employees have been subject to disciplinary action. There is no detail about the nature of the disciplinary action that was taken, but in its disclosure, the MoD said that in the majority of the cases, the incidents were “less serious” and involved unauthorised disclosure.
The likely sanction in such cases, it added, was some form of disciplinary action “proportionate to the severity of the incident.”
The disclosed figures only take into account incidents which have been investigated and brought to close.
Indeed, the MoD has said that the number of staff disciplined between January 2020 and this May may be even higher with several cases still under review.
Similarly, the figures detailed by the MoD only refer to civil servants or service personnel. It is unclear whether any external contractors were subject to similar disciplinary measures.
Stewart McDonald MP, the SNP’s defence spokesman, said: “This is a truly worrying development that needs to be treated with the utmost seriousness and transparency. That it comes just weeks after sensitive documents were found at a bus stop makes it all the more incredible.
“The MoD must answer to parliament and the public for these leaks, and must ensure robust mechanisms are in place to prevent leaks of sensitive information that may harm national security - it is in all our interests that this is done properly.
“Going forward it would be wise for the MoD to revisit its policies and procedures in these areas, in full consultation with parliament, to ensure that the current weak processes in place are made robust and fit for the 21st century.”
A spokeswoman for the MoD said: “None of the incidents referenced compromised national security and the majority were minor breaches of the MoD’s social media policy.
“We take all unauthorised disclosures of information extremely seriously. Every incident is investigated and mitigations are put in place to prevent reoccurrences.”
While there is no detail of the information that was leaked, an analysis of the MoD’s annual reports in recent years shows spike in the number of so-called ‘personal data related incidents’, where data was either lost, disclosed without authorisation, or disposed of insecurely.
There were just 68 incidents in 2016/17, rising to 117 in 2017/18 and then 463 in 2018/19. The latest tally, covering 2019/20, saw 546 incidents.
Seven of the incidents were considered serious enough to be reported to the Information Commissioner’s Office. They included the loss of criminal investigation filed during archiving.
The figures show there were 49 instances of inadequately protected electronic equipment, devices, or paper documents being lost from secured government premises.
All MoD personnel are mandated to receive a full security briefing, or take an annual course in security fundamentals.