THE PSNI has launched an investigation after the force released a document containing details of all serving officers and staff.
The spreadsheet was published on a legitimate Freedom of Information (FoI) website on Tuesday.
The Police Federation of Northern Ireland, as well as political parties in the North, have called for answers over the release, which the PSNI is treating as a 'critical incident'.
It comes at a time when the threat level in relation to Northern Irish related terrorism sits at Severe, meaning an 'attack is highly likely'.
Serious breach
The spreadsheet, which was released following a routine FOI request, inadvertently included the surname, initials, rank/grade, role and location of all serving officers and staff.
It was available to view on the website for three hours before it was removed.
"As a service we are acutely aware of the seriousness of this breach and have declared it to be a critical incident," said Assistant Chief Constable Chris Todd, Senior Information Risk Owner.
"We fully understand the very real concerns being felt by our colleagues and their families and we are working hard to do everything we can to mitigate any risk.
"We are working with our security partners and organisations to investigate this incident."
The force has issued updated personal security advice to all officers and staff and established an emergency threat assessment group to look at the welfare concerns of those involved.
An Independent Advisor is due to conduct a review of PSNI processes to determine how the breach happened what can be done to prevent similar incidents.
Meanwhile, the Chief Constable is returning early from holiday to attend a special sitting of the Northern Ireland Policing Board on Thursday.
'Breach of monumental proportions'
Liam Kelly, Chair of the Police Federation for Northern Ireland, said the breach could do 'incalculable damage'.
"This is a breach of monumental proportions," he said.
"Even if it was done accidentally, it still represents a data and security breach that should never have happened.
"Rigorous safeguards ought to have been in place to protect this valuable information which, if in the wrong hands, could do incalculable damage.
"The men and women I represent are appalled by this breach. They are shocked, dismayed and justifiably angry.
"Like me, they are demanding action to address this unprecedented disclosure of sensitive information."
He added that new safeguards are required to prevent a repeat incident.
'Critical systems failure'
The SDLP and Sinn Féin have both expressed their concerns over the matter.
SDLP Policing Board member Mark Durkan said the breach should never have been allowed to occur.
"It is inconceivable that any single member of staff would have the ability to download a detailed database with such sensitive information," he said.
"This represents a critical systems failure and must be addressed immediately."
Sinn Féin counterpart Gerry Kelly called the breach 'unprecedented', particularly in the wake of the attempted murder of a PSNI officer in February.
"There is an emergency Policing Board meeting on Thursday," said Mr Kelly.
"I will be asking why safeguards were not in place to prevent such a breach happening and how quickly measures can be put in place to ensure it won't happen again.
"In circumstances where the level of threat is at severe after the attempted murder of DCI John Caldwell there will be huge concern among members of the PSNI and their families and the wider community at this revelation."
