The publication of Sir Desmond de Silva's report into the killing of Pat Finucane sparked renewed calls for a public inquiry into the 1989 murder.
But there was also concern over the damage it might inflict on the armed forces, with Lord King, the Conservative peer who was Northern Ireland secretary at the time of Mr Finucane's death, saying the British Army's reputation was "at stake".
Labour leader Ed Miliband told the Commons: "Anyone reading this report will believe it is an appalling episode in our history. All sides of the House believe that we must establish the full and tested truth about Pat Finucane's murder but on this side of the House we continue to believe that a public inquiry is necessary for his family and Northern Ireland."
Sinn Fein MP for West Belfast Paul Maskey said the report "does reinforce the need for an independent inquiry because of some of the serious issues it does highlight... It doesn't state who had the responsibility, for example, for recruiting some of these people... The British Army itself, the British Government have the responsibility to own up and tell us who it is that they are protecting, because the de Silva report is protecting somebody".
But Lord King said the incident involved a serious breach of orders by only "a few" military and security personnel. The former Northern Ireland secretary and defence secretary told BBC Radio 4's World At One: "There was a very strict Army instruction that they were not to get involved in anything illegal... They quite clearly did. There was quite clearly a breach of the instructions at the time and that's the seriousness of it."
He added: "This has revealed a very serious situation in this case. What is so serious about it is that it impugns the RUC and the UDR and the British intelligence, security and British Army when in fact the majority of the people involved were extremely brave. Why this has got to be addressed is that the reputation of the British Army is at stake and this is a very serious mistake that was made and a tragic outcome as well."
Peter Hain, Northern Ireland secretary from 2005-07, told the BBC: "When you look at the detail, including what the Prime Minister revealed to Parliament, I think that provides the basis for a lot of follow-up. Whether we subsequently have an inquiry or not, there is a question of whether prosecutions should follow, there is a question also of acknowledging and learning the lessons from this, to make sure that nothing like this can ever happen again."
The SDLP's Mark Durkan told MPs: "Many of us find it hard to leave these matters just simply to the interpretations and the inferences that Desmond de Silva has drawn from the dreadful evidence that he has produced... If we are going to get to the bottom of this, we have to get to the top of it and Desmond de Silva's trying to tell us 'No, there was no top'."
Democratic Unionist MP Ian Paisley backed Mr Cameron's refusal to hold a public inquiry and repeated the call for the Dublin government to open its files. He told the Commons: "There is more than a shred of evidence that the Republic of Ireland's government armed the Provisional IRA and there should be an investigation into that and honesty about that, so as we see all of the picture."
An Army spokesman said: "We are very grateful for the report's detailed analysis of the circumstances leading to the death of Patrick Finucane. Many of the lessons from this period have been reflected in legislation and procedures now considered standard in modern behaviour. Once we have had the opportunity to read the report's recommendations in detail, we will ensure that we make any further changes necessary and report back accordingly."