Scotland Yard will investigate reports that officers secretly bugged meetings which they held with murdered teenager Stephen Lawrence's friend Duwayne Brooks and his lawyers.
The BBC quoted a senior police source as saying authorisation had been given for two meetings between Mr Brooks, his legal representatives and investigating officers to be recorded.
A solicitor for Mr Brooks - who was with Mr Lawrence on the night he was killed in a racist attack in Eltham, south London, in 1993 - described the latest allegations as "sinister" and called on the Met to come clean about its activities against her client. It follows claims by former undercover officer Peter Francis that he was tasked with finding information to smear Mr Brooks or the Lawrence family and their campaign for justice for their son.
Scotland Yard confirmed that it had received a letter from Mr Brooks's solicitor, Jane Deighton, which had had been referred immediately to Deputy Assistant Commissioner Fiona Taylor, the head of its directorate of professional standards (DPS).
"An investigation into the circumstances of what took place has now been started by the DPS," it said in a statement. "This investigation will seek to establish exactly what was authorised and what happened to any material which may have been gathered, in the context of the legal framework of that time."
The bugged meetings with Mr Brooks and his lawyers were said to have taken place in the offices of solicitors Deighton Guedalla in Islington, north London, in 1999 or 2000. Ms Deighton, who was present at one of the meetings, said the police had asked for the meeting so they could brief Mr Brooks about the progress in the murder investigation.
They came after the Macpherson Inquiry into Mr Lawrence's murder concluded that the police treatment of Mr Brooks had been racist. The murder investigation had been taken over by Deputy Assistant Commissioner John Grieve in an attempt to inject new impetus into the hunt for the killers.
Ms Deighton said she could see no reason for police to record covertly the meetings which they had themselves requested.
"There is absolutely no rational reason. That is very worrying for Duwayne Brooks and for ourselves because it is quite sinister," she told BBC Radio 4. "Why covertly record a meeting that you have asked for? Why unless it is part of something much bigger, why unless in fact covert recordings were happening of Duwayne Brooks and ourselves in different situations? That is what we want to know."
Mr Francis has previously said that information he gathered led to Mr Brooks being arrested and charged in October 1993 before the case was thrown out by a judge as an abuse of process. Ms Deighton said that Mr Brooks now needed to know exactly what the police had been doing to him over the past 30 years.