The police watchdog is investigating claims that one of Britain's most senior policemen met an undercover officer who spied on the Stephen Lawrence family.
The Independent Police Complaints Commission (IPCC) said it had started an investigation into allegations of "discreditable conduct and breaches of honesty and integrity" on the part of Metropolitan Police commander Richard Walton.
He was temporarily removed from his job as head of the counter-terrorism command SO15 in March following the publication of Mark Ellison QC's report into the original Lawrence murder investigation.
Mr Ellison revealed that an undercover officer - known as N81 - held a meeting in 1998 with Mr Walton, who was then an acting detective inspector working on Scotland Yard's Lawrence review team, responsible for making submissions to the Macpherson Inquiry.
The IPCC said it will also investigate allegations of discreditable conduct by two former officers, then-detective inspector Robert Lambert and Commander Colin Black, who were both identified in the review as having played a part in facilitating the meeting with the undercover officer.
Mr Walton is alleged to have met an undercover officer in 1998 and "obtained information pertaining to the Lawrence family and their supporters, potentially undermining the inquiry and public confidence", the IPCC said.
It is also alleged that Mr Walton provided inconsistent accounts to Mr Ellison's review team regarding his actions, the watchdog added.
IPCC deputy chair Sarah Green said: "Mark Ellison's review highlighted a number of extremely serious matters which strike at the heart of public confidence in the police.
"Following the review, I asked the MPS (Metropolitan Police Service) to consider whether the conduct of any officers or former officers should be recorded and referred to the IPCC.
"Having now received referrals in relation to all three of the above officers and, in view of the seriousness of the matter and the significant public interest, I have determined the IPCC should conduct an independent investigation. I have notified Mr Lawrence and Baroness Lawrence of this decision."
Following the IPCC's decision, Mr Walton: "I welcome the decision to investigate this matter independently and the IPCC will have my full support."
Aspiring architect Stephen was murdered at the age of 18 by racists in Eltham, south-east London, in April 1993 and it took nearly 20 years for two of the gang of up to six killers to be brought to justice.
The Ellison report disclosed that in the late 1990s, N81 infiltrated a group which then sought to influence the Lawrence family campaign to further its own agenda.
Feedback from N81 to his unit, the Special Demonstration Squad (SDS), touched on personal details concerning the Lawrence family, such as comments on the separation of Stephen's mother and father, Doreen and Neville.
A meeting was set up between N81 and Mr Walton, which was described as a "fascinating and valuable exchange of information".
In the wake of Mr Ellison's review, Home Secretary Theresa May ordered a judge-led public inquiry into the SDS and announced the creation of a new criminal offence of police corruption.
The Ellison review also found that one of the officers on the original investigation into Stephen's death, detective sergeant John Davidson, may have acted corruptly.
It was claimed that Davidson had admitted having a "corrupt connection" with Clifford Norris, the gangland boss father of David Norris, who was finally convicted of Stephen's murder in 2012 alongside Gary Dobson.