The names of 42 dead children were used as fake identities by undercover officers but their families have not been informed because of the "risk" to police, a report said today.
Derbyshire Chief Constable Mick Creedon, who is leading a probe into the activities of undercover police, said that the relatives deserve an apology but revealing the names used "would and could put undercover officers at risk".
So far 40 officers have been interviewed as part of Mr Creedon's investigation, called Operation Herne
The identities were of children born between 1940 and 1975, and officers used the names of children aged between four and eight.
Mr Creedon's report on the use of deceased children's names, published on Tuesday, also revealed that the practice could have been used outside of Scotland Yard's Special Demonstration Squad (SDS) and the National Public Order Intelligence Unit (NPOIU), by police officers and possibly the security services.
The report said: "It is a fact that undercover officers working in the field of serious and organised crime also need to establish secure covert identities, create legends, obtain documentation and if necessary withstand invasive scrutiny by their targets.
"It would be a mistake to assume that the identities of dead children were used solely by the SDS and the NPOIU and the possibility is that the tactic was more widely used."
Metropolitan Police Commissioner Sir Bernard Hogan-Howe apologised for the shock and offence caused by using the fake names and said that this had been passed on to one family who discovered their child's identity had been used.
So far, investigators have discovered 106 covert names that used by the SDS between 1968 and 2008, 42 of which are believed to have been based on the details of dead children. Another 45 were fictitious, and the rest have not yet been categorised.
The report said informing the families must be balanced with officers' safety and the standard practice of "neither confirm nor deny" (NCND), used by police officers to avoid revealing information which might compromise intelligence sources.
It said: "The question has to be addressed as to whether the parents or family members of those deceased children whose identities were used should be contacted and told of what was done.
"Whilst there is a strong argument that the families should be contacted, this needs to be balanced against the long-established NCND policy, the ongoing duty of care to the officers, the significant oprational security considerations and the potential impact on elderly family members who may have dealt with their bereavement decades earlier."
Mr Creedon was brought in to lead an independent probe into Scotland Yard's SDS in February this year. His team will now examine the activities of the NPOIU.
So far the investigators have received 14 inquiries from 17 families who believe they may have been affected.
The earliest confirmed officer to have used such an identity was in the field between 1976 and 1981, the report said.
The practice was phased out from 1994 in the SDS, but potentially used by the NPOIU up to 2003.
The report said: "A range of officers at different ranks and roles have been interviewed by the investigation team. The information provided corroborates totally the belief that for the majority of the existence of the SDS the use of deceased children's identities was accepted as standard practice."
Simon Ray QC, Legal Advisor to the Crown Prosecution Service concluded that it is unlikely any criminal charges could be brought against the officers for using the identities.
Mr Creedon said that the practice is no longer used.
Sir Bernard said: "I believe the public do understand the necessity for police and others to do things like this to protect against a much greater harm. It was never intended or foreseen that any of the identities used would become public, or that any family would suffer hurt as a result. At the time this method of creating identities was in use, officers felt this was the safest option.
"I absolutely agree with Chief Constable Creedon that the Metropolitan Police should apologise for the shock and offence the use of this tactic has caused. My officers have this morning passed on that apology directly to one family, which has been told its child's identity may have been used, and 14 families who have contacted us to ask whether this may have happened."
But Jules Carey, solicitor for Barbara Shaw who fears that her son Rod Richardson's name was used, said she feels her concerns have been "swept under the carpet".
He said: "What we heard this morning was not an apology but a PR exercise. The families of the dead children whose identities have been stolen by the undercover officers deserve better than this. They deserve an explanation, a personal apology and, if appropriate, a warning of the potential risk they face, in the exceptional circumstances, that their dead child's identity was used to infiltrate serious criminal organisations.
"The harvesting of dead children's identities was only one manifestation of the rot at the heart of these undercover units which had officers lie on oath, conduct smear campaigns and use sexual relationships as an evidence-gathering tool.
"In Ms Shaw's case, the Metropolitan Police have stated that the investigation into her complaint is complete but they have declined to provide her with a report on the outcome. They have refused to confirm or deny that the identity of her son was used by an undercover officer despite there being only one Rod Richardson born in 1973. And they have concluded that there is no evidence of misconduct or even performance issues to be addressed.
"Ms Shaw has told me that she feels her complaint has been 'swept under the carpet" and she has instructed me to appeal this outcome.
"It is clear that the public have no reason to be reassured either by today's announcement or the hotchpotch of an investigation into the deployment of undercover police officers, where the police have effectively been left to investigate themselves."
Additional reporting by PA