The surnames, initials, work location and department of each staff member were made public after they were included in error in response to a freedom of information request, and published on the requestor’s website for around 2.5 hours.

The accidental release was hugely sensitive in Northern Ireland, where police officers are still sporadically targeted by dissident groups in bomb and gun attacks, despite a 1998 peace deal largely ending three decades of sectarian violence in the province.

“We have issued updated personal security advice to all of our officers and staff and have established an emergency threat assessment group,” the Police Service of Northern Ireland (PSNI) said in an update.

“As well as general advice on safety and security this multi-disciplinary group will focus on immediate support to those with specific circumstances which they believe place them or their families at immediate risk or increased threat of harm.”

They described the data leak as an “extremely serious situation”.

The Police Federation for Northern Ireland, which represents officers, has described the data release as especially sensitive as many “go to great lengths and do everything possible to protect their police identity and role”.

Britain’s MI5 intelligence agency increased the threat level in Northern Ireland from domestic terrorism to severe – meaning an attack is highly likely – after an off-duty officer was left seriously wounded in February following a gun attack by the new IRA, one of the small militant groups opposed to peace.

The PSNI said it had sought help from an independent advisor to conduct a review “in order to understand what happened, how it happened and what we can do immediately to prevent such a breach happening in the future”.