The Special Branch withheld crucial information from detectives in Northern Ireland investigating an IRA murder, a report revealed today.
Eoin Morley was gunned down at his girlfriend's home in Newry, Co Down, on Easter Sunday 1990 amid tensions between the IRA and the Irish People's Liberation Organisation, a splinter republican paramilitary faction.
The victim's family have claimed officers protected the gunman.
Even though the RUC built up high-grade intelligence on those suspected of plotting Mr Morley's shooting, the Northern Ireland Police Ombudsman, Mrs Nuala O'Loan, discovered no one was ever arrested.
Police were also unable to tell Mrs O'Loan who took charge of the inquiry. After examining files on the 1990 killing, which was linked to a dispute among republicans, Mrs O'Loan found no evidence to back claims it was planned by the RUC.
But her examination of Special Branch files uncovered 10 separate items of information which may have been vital to the murder investigation yet were never passed on to detectives. The anti-terrorist unit's failures were unacceptable, the report found.
Mrs O'Loan said: "In the absence of any indication as to who held the information and why, it has not been possible to draw any conclusions, other than to say this was but one of many occasions on which intelligence held in headquarters, which was relevant to the investigation of the most serious of crimes, was not transmitted to those police officers carrying out investigations."
The latest investigation comes after relatives of Mr Morley (23) alleged police instigated the murder in an attempt to ignite a republican feud and refused to arrest the chief suspect.