A public inquiry is to be launched into the role of undercover officers following the "profoundly shocking" revelations that police spied on Stephen Lawrence's family after his murder.
Home secretary Theresa May announced a judge-led inquiry following the publication of a major review looking into alleged police corruption in the original Lawrence murder inquiry.
The report by Mark Ellison QC found that Scotland Yard had planted an officer, named only as N81, to spy on the Lawrences by infiltrating an activist group close to them in the run-up to the public inquiry.
The report also suggests there is evidence one of the detectives involved in the original murder investigation was corrupt.
It said Det Sgt John Davidson may have had a "corrupt relationship" with Clifford Norris, the father of David Norris, who was convicted of the murder of Lawrence along with Gary Dobson in January 2012. Those allegations were not disclosed during previous inquiries.
The Ellison review said it had found no other allegations of corruption of other officers but did not discount the possibility.
Lawrence was 18 when he was stabbed to death by a racist gang in southeast London in 1993.
The Ellison report criticised the Metropolitan Police for arranging a meeting between N81 and an officer employed to respond to the MacPherson inquiry into the force's handling of the murder.
Ellison described the meeting as "wrong-headed" and "inappropriate" and was arranged so police could have a "secret advantage" in the inquiry by the Special Demonstration Squad (SDS) undercover deployment.
Ellison said: "The reality was that N81 was, at the time, an MPS [Metropolitan Police Service] spy in the Lawrence family camp during the course of judicial proceedings in which the family was the primary party in opposition to the MPS.
"The mere presence of an undercover MPS officer in the wider Lawrence family camp in such circumstances is highly questionable in terms of the appearance it creates of the MPS having a spy in the family's camp."
N81 was employed to uncover "tactical information" about Lawrence's parents, Doreen and Neville. The report said had this information been made public at the time it could have resulted in "serious public disorder".
Ellsion continued: "There was no conceivable public order justification for this meeting. Nor was there any other discernible public benefit, and certainly none that could possibly outweigh the justifiable public outrage that would follow if the fact of the meeting had been made public when the inquiry resumed in September 1998."
Following the report's publication, Neville Lawrence said: "What the Home Secretary has announced today is 21 years overdue. Mark Ellis's report has simply corroborated what I have known for the past 21 years and our long fight for truth and justice continues."
A Met Police spokesperson said: "Mark Ellison QC has received the full support of the Metropolitan Police Service in the research for his report.
"As we have only just received a copy of his report it would be highly inappropriate to comment upon it until we have taken the time to fully read, understand and assess its content.
"His report considers some very serious issues that whilst in the main are historical, could have a negative impact on confidence in modern-day policing. We await the home secretary's announcement on how she wishes Mr Ellison's work to be taken forward."
Prime minister David Cameron tweeted: "Like the Home Secretary, I find the conclusions of the Stephen Lawrence review profoundly shocking. It's important we have a full inquiry."