Four retired police officers are considering legal action against NI Police Ombudsman after their personal details were leaked.
The leak came to light following the arrest of an former ombudsman investigator over an alleged theft of sensitive security documents.
A lawyer for the officers said the Police Ombudsman had confirmed personal details were unlawfully disclosed.
Police have begun a criminal investigation.
It is understood the documents contained information the police and security service MI5 believe could put the lives of individuals at risk but do not refer to any case currently being investigated by the Police Ombudsman.
The lawyer said his clients disputed claims that the leak was connected to a historic case and said there was a link to an ongoing ombudsman inquiry.
A 69-year-old man was arrested in Dartford, Kent, on Sunday after detectives from the PSNI's Serious Crime Branch conducted a joint search with local police.
It is understood he retired from the ombudsman's office a number of years ago and that the documents do not refer to any case currently being investigated by it.
The Police Federation of Northern Ireland (PFNI) has called for a "full inquiry" into the operation of the police ombudsman and said it was an "astounding and very worrying state of affairs".
Mark Lindsay, chair of the federation, said there had to be an element of fairness for police officers under investigation.
"They need the same protections that a normal member of society would have and that doesn't exist at the moment with the ombudsman's office," he told the BBC's Good Morning Ulster programme.
"There is a real role for the Police Ombudsman's office, but that office has to hold the confidence of police officers."
Police have also suspended the release of any further sensitive material to the ombudsman's office until a review of security protocols is carried out.
The Ulster Unionist MP Tom Elliott said the ombudsman's office had serious questions to answer.
"When there's alleged wrongdoing, the PSNI should be called in at an earlier stage to investigate these matters so that they can be independently investigated," Mr Elliott said.
"There is a failure and a gap there that needs to be resolved."
In a statement to the BBC, a spokesman for the ombudsman confirmed he was alerted by police last week about the theft of sensitive material originating from the office.
The office of the Police Ombudsman said it was anticipated that this suspension of the sharing of sensitive material "will be temporary".