The MoJ has sacked four members of staff and issued final warnings to a further three, while Scotland Yard has started disciplinary action against 27 Metropolitan (Met) police officers. Both organisations ban staff from personal use of social networks during working hours.
The MoJ also revealed 41 staff had been disciplined for breaches of IT security policy, covering misuse of email, web browsing and incorrect use of passwords and login details.
"Although these departments have rules in place regulating the use of social networking sites by personnel, data breaches are still occurring and more needs to be done to prevent them," said Keith Crosley, director at email security specialist Proofpoint.
"It is worrying that so many personnel who work in two of the UK's leading law-enforcement agencies are bringing them into disrepute, if not risking operational security by the way they conduct themselves online."
Proofpoint said its own research found 17 percent of organisations have investigated a leak of confidential information via a social networking site, while 10 percent have disciplined an employee for violating social networking policies in the past year.
"The Met and MoJ need to be far more vocal about policies that are already in place and the punishments for not following the rules," said Crosley
Scotland Yard has issued a nine-point guide advising officers not to disclose they are police, compromise themselves or the force or bring the service into disrepute if using social networking sites in their own time.
It also said if staff disclose that they work for the Met, then they are told it must be made absolutely clear that any views expressed do not represent the official position of the force but are the views of the individual.
The Met said all police officers and staff are expected to adhere to the MPS Information Code of Conduct which sets out the policy on the use of MPS Information and information communication and technology systems.
"The MPS Directorate of Information issues regular reminders to staff on the importance of ensuring they comply with this policy."
The MoJ said staff can only access social networking sites for professional reasons if they are able to provide a strong business case that shows they need to use these media to perform their role.