Sir John Stevens has said he has found evidence of widespread collusion between the security forces and loyalist paramilitaries in the murder of Catholics. However, he declined to say the collusion was institutionalised.
He said it wasn't his job to state whether there should be a public inquiry. He said he had "uncovered enough evidence" to believe two loyalist killings could have been prevented.
They were the 1989 murder of Catholic solicitor Mr Pat Finucane, and that in 1987 of Protestant student Mr Adam Lambert, who was mistaken for a Catholic.
"I also believe the RUC investigation of Pat Finucane's murder should have resulted in the early arrest and detection of his killers. I conclude there was collusion in both murders and the circumstances surrounding them." He said a former British government junior minister, Mr Douglas Hogg, was "compromised" after he told the House of Commons just weeks before Mr Finucane's murder that some solicitors were "unduly sympathetic to the IRA" .
This was Sir John's third investigation and he said the collusion he had now uncovered was at a level "way beyond" that which he had discovered during his first report.
He likened his investigation to "going into one room and seeing the content and seeing another door at the other side of the room, opening that door and getting into a new environment".
He said his three investigations had been "wilfully obstructed and misled". "From day one, this obstruction was cultural in its nature and widespread within parts of the army and RUC, the Force Research Unit, and RUC Special Branch in particular".
Rumours and counter-rumours had been circulated "deliberately designed to throw us off course".
He said the inquiry had been the biggest investigation of its kind to be held in the UK. "It should not have taken years to get to the point we are now.
"None of us are above the law and no future inquiry should have to be conducted in the way we have had to conduct ours." He said he would be returning in January to see if his 21 recommendations had been implemented.
"My inquiries have highlighted collusion, the wilful failure to keep records, the absence of accountability, the withholding of intelligence and evidence, and the extreme of agents being involved in murder.
"These serious acts and omissions have meant that people have been killed or seriously injured. Informants and agents were allowed to operate without effective control and to participate in terrorist crimes.
"Nationalists were known to be targeted but were not properly warned or protected. Important evidence was neither exploited nor preserved." Sir John said the report released to the media could not go into "the detail you would like" because of the ongoing nature of his investigations and further possible criminal charges and prosecutions.
The families of some of those whose loved ones were killed in the controversial killings were angry when they were barred from the press conference. Police officers dragged one woman away from the room.
Mr Mark Thompson of Relatives for Justice said: "It is an absolute disgrace that the families who have been bereaved and who are being discussed in this report have been excluded.
"It is bad enough that only around 20 pages of this document is being published without us having to ensure this sort of treatment." The families were later given access to detectives from the Stevens Inquiry but they said their request to meet Sir John was denied.