The report found no evidence of a direct role in the car bomb attack 12 years ago, but said it could not rule out the possibility of involvement by a rogue element of the security forces.
The inquiry, which cost £46.5 million, concluded that Royal Ulster Constabulary (RUC) officers publicly abused and assaulted the solicitor, and it believed police intelligence on the 40-year-old mother of three had leaked out.
Before her death on 15 March 1999, the lawyer, who worked on a number of controversial cases including those of suspected republican terrorists, had alleged police intimidation.
Those claims gained international attention and the report found that police had made "abusive and threatening remarks" about the solicitor. The inquiry found that the state "failed to take reasonable and proportionate steps" to safeguard her life.
The current chief constable of the Police Service of Northern Ireland (PSNI), Matt Baggott, apologised for police failings.
Presenting the report to the House of Commons, Secretary of State Owen Paterson said: "I am profoundly sorry that omissions by the state rendered Rosemary Nelson more at risk and more vulnerable. It is also deeply regrettable that despite a very thorough police investigation no one has been charged for this terrible crime."
The 700-word report included two and a half pages of conclusions which list its key findings. It said it believed that RUC intelligence on Mrs Nelson had leaked out and, whether the information was correct or not, this had "increased the danger to Rosemary Nelson's life".
The report authors also believed claims made by Mrs Nelson before her death that police had threatened her during interviews with her clients. They added: "This became publicly known and would have had the subsequent effect of legitimising her as a target in the eyes of loyalist terrorists.”
Garvaghy Road Residents Coalition responds to Report
The Garvaghy Road Residents Coalition has responded to the Report of the Rosemary Nelson Inquiry in the statement below:
"We are conscious that Rosemary was first and foremost a mother, a wife, a sister and a daughter. As such the thoughts of many within our community will lie with Rosemary's family today.
"Likewise, due to the brutal circumstances of her death, all the other work which Rosemary became involved in is too often forgotten and overlooked. Less well known is her work for the Travelling community; on women's rights; in opposing discrimination in the workplace; and on behalf of the Irish language. Rosemary worked with many voluntary and community groups and with local schools in the Lurgan/Portadown area.
"In responding to today's report, we are mindful that Judge Peter Cory, in his various reports which led to the establishment of this inquiry into Rosemary Nelson's murder, set out a clear definition of what constituted collusion.
"Judge Cory said that "Because of the necessity for public confidence in the Government agencies, the definition of collusion must be reasonably broad when it is applied to these agencies. That is to say that they must not act collusively by ignoring or turning a blind eye to the wrongful acts of their servants or agents by supplying information to assist those servants or agents in their wrongful acts or by encouraging others to commit a wrongful act. Any lesser definition would have the effect of condoning or even encouraging state involvement in crimes.”
"It is clear that had the members of the Inquiry team borne this definition in mind then the conclusions which they reached would have been entirely different.
"Nevertheless, a full reading of the report and the many incidents, threats, acts of omission, and hostile attitude of the RUC and NIO evidenced within the report confirms, when measured against Cory's definition, that there was indeed collusion in Rosemary's murder.
"Furthermore, the assertion within the report that a rogue member or rogue members of the RUC, British Army or other British intelligence agencies may in some way have assisted those directly involved in Rosemary's murder is a totally discredited defence. It was a defence that was continually rolled out by the British government and others during the 1970's, 1980's and 1990's.
"Too often the defence of "a few bad apples" within the RUC and British military was used by the state to excuse the direct involvement of its personnel in many sectarian attacks across the North.
"That the Inquiry chose to repeat such a lame and discredited pretext as a possible explanation for Rosemary's murder will in no way lessen the widely held belief of direct and official British involvement in her murder."