Said a former officer yesterday: "There are really only a few reasons that files would be forwarded to the [Attorney-General's] office - in criminal offence terms, really only treason and bribing a police officer.

"Conspiracy to pervert the course of justice, or malfeasance in public office, wouldn't merit his consideration.

"If the case is overly-complicated, it might go to the A-G, but, then, there have been even more complicated cases - some involving fatal shootings over the last 35 years - so it's difficult to see this being too complex for the Director of Public Prosecutions in Belfast.

"The only other possibility, really, is the sensitivity issue, or political considerations.

"Is it possible that the Ombudsman has found some trace or lead to Box [MI5] which even we don't know about or never suspected?

"What we say is that we have not committed any criminal offences and that we carried out our duties in accordance with Government policy and observed the provisions of the Regulation of Investigatory Powers Act.

"It was RUC Special Branch officers who created the model for the guidelines incorporated into RIPA and that is what was followed at the management level."

The former officer said it may also be that forwarding the papers to the Attorney-General's office was designed to spare Mrs O'Loan " embarrassment".

"If the Public Prosecution Service in 2005 or 2006 declared that there was no basis for criminal charges to be brought against any former Special Branch officer, then Mrs O'Loan's report would be a bit of a damp squib, wouldn't it?

"In November, for instance, we understand that she was advised by her lawyers that she couldn't, or shouldn't, name the primary subject of her report, because his relatives might sue her for putting his life in jeopardy if he was subsequently killed by the UVF," he said.

"That's why there was a delay and why he will not be named in the report that is made public.

"We will wait to see what it says before making any further comment."