British police and army agents planted inside Northern Ireland's major Protestant gang played a pivotal role in assassinating a Belfast attorney, a former United Nations war crimes investigator concluded in a damning report published Wednesday into one of the most divisive slayings of the entire four-decade conflict.

Sir Desmond de Silva concluded in his approximately 800-page report that the 1989 killing of Pat Finucane probably would never have happened without key input from state agents within the Ulster Defence Association, the militant group that killed the 38-year-old Catholic lawyer in front of his wife and three children.

'It is really shocking that this happened in our country.'—Prime Minister David Cameron

De Silva, a human rights lawyer appointed by the British government in October 2011 to produce the report, said members of the Northern Ireland police's anti-terrorist Special Branch and the army's Force Research Unit knew Finucane was a target, and even recommended him to UDA assassins as one because he specialized in defending Irish Republican Army suspects. Both units since have been disbanded as part of wider security reforms and peacemaking efforts in Northern Ireland.

De Silva wrote that police and army handlers of agents within the West Belfast UDA probably could have stopped the attack but instead "actively furthered and facilitated his murder" and mounted "a relentless attempt to defeat the ends of justice."

Sinn Fein's Gerry Adams and Mary Lou McDonald speaking to the media outside Leinster House, the home of the Irish Parliament, reacting to the de Silva report into the 1989 murder of Belfast solicitor Pat Finucane. (Julien Behal/AP Photo)

British Prime Minister David Cameron and leaders of Northern Ireland's Protestant majority lauded de Silva's findings as comprehensive and compelling, particularly his decision to publish hundreds of previously secret army and police reports, although in censored form blacking out all the names of officers and paramilitary contacts.

"'When you read some of the specific cases in the report … it is really shocking that this happened in our country," Cameron told lawmakers as he summarized the report. He repeated a public apology to the Finucane family which he had first given on the day he appointed de Silva last year.

But Irish Catholic leaders and Finucane's family dismissed the findings as old news and a coverup of the full picture. They were most critical of de Silva's judgment that the British government of the day — led by Margaret Thatcher — had not ordered, or in any way encouraged, police and army anti-terrorist officials to collude with the UDA in targeting IRA members and supporters.

Catholic leaders and the family renewed calls for a public inquiry led by a judge that would compel former British government ministers and senior retired security officials to testify. Cameron has ruled this out, citing the exceptional cost and glacial pace of similar probes in Northern Ireland.

'A whitewash'

"This report is a sham. This report is a whitewash. This report is a confidence trick dressed up as independent scrutiny," said Geraldine Finucane, who was shot in the foot while trying to stop two UDA gunmen from firing 14 bullets into her husband in the dining room of their Belfast home on Feb 12, 1989. She has spent the past 23 years seeking full disclosure of the state collusion involved in the killing.

She noted that de Silva broadly exonerated government ministers with oversight of Northern Ireland security in the 1980s and the only anti-terrorist agency still in existence in Northern Ireland, the domestic spy agency MI5.

Most blame fell instead on the police's disbanded Special Branch unit, which had two UDA members involved in the killing on its informer payroll: William Stobie, who supplied the guns, and Ken Barrett, who in 2004 pleaded guilty to being one of the gunmen.

And de Silva found that the army's disbanded Force Research Unit had the inside story on most, if not all, of the UDA's planned murder targets because it had positioned an employee, Brian Nelson, as the UDA's director of intelligence responsible for researching targets. He said at least 85 per cent of the UDA's information on targeting IRA members and supporters came from army sources.

He said officials in both state intelligence-gathering units did nothing to stop a series of UDA killings.

Widow: state favoured

Stobie was killed in 2001 by UDA colleagues after he testified to a previous investigation into the Finucane case. Nelson died of cancer in 2003. Barrett, the only person convicted for the Finucane murder, received a 22-year prison sentence but was paroled after just two years under terms of Northern Ireland's peace accord.

"At every turn, it is clear that this report has done exactly what was required: to give the benefit of the doubt to the state, its Cabinet and ministers, to the army, to the intelligence services, to itself," Geraldine Finucane told a press conference, flanked by her sons Michael and John, who both witnessed their father's killing and are human rights lawyers today.

"At every turn, dead witnesses have been blamed and defunct agencies found wanting. Serving personnel and active state departments appear to have been excused," she said.

Catholic leaders likewise said they found it hard to believe that no government minister in the late 1980s knew what was going on. They pointed to an infamous statement made by former government minister Douglas Hogg, in the Commons one month before Finucane's killing, that some lawyers in Northern Ireland were "unduly sympathetic to the IRA." De Silva said he found no evidence from government and police files that Hogg or other government ministers had any forewarning of the attack on Finucane, and cited instead evidence that ministers sought to have Nelson prosecuted for murder.

"The prime minister must know that if we are to get to the bottom of this, we have to get to the top of it. And Desmond de Silva is trying to tell us: No, there was no top," Mark Durkan, a lawmaker who represents moderate Catholic opinion in Northern Ireland, told Cameron during the House of Commons debate on the report.

3 secrecy-shrouded probes

Finucane's case is one of the most heavily investigated killings of the Northern Ireland conflict, which has claimed some 3,700 lives since 1969.

Three secrecy-shrouded probes led by former London police commissioner John Stevens previously identified Nelson as an army agent and Stobie and Barrett as police informers within the UDA.

His first probe exposed Nelson, who in 1992 pleaded guilty to 20 criminal charges, including conspiracy to murder, but not directly to involvement in the Finucane killing. He died six years after his 1997 parole.

Stevens' final investigation in 2003 spurred Barrett's confession and conviction. Stevens said his three probes in total produced 9,256 written statements, 10,391 documents exceeding 1 million pages, and 16,194 exhibits of potential evidence — virtually none of it made public, all of it open for de Silva to examine.

The UDA killed more than 250 people, mostly Catholic civilians, before calling a 1994 ceasefire, renouncing violence in 2007, and disarming in 2010. But the outlawed group still exerts influence today in many working-class Protestant communities, and police say scores of UDA members have helped stoke street clashes with police over the past week in Belfast and several predominantly Protestant suburbs. About 30 police have been injured and 30 Protestant militants charged with rioting.