The mother of Ricky Reel, who has been campaigning for an inquest into her 20-year-old son's death in Kingston in 1997, was spied on by undercover Metropolitan Police officers, it has been claimed.
Sukhdev Reel told the BBC she was informed by an officer from Operation Herne - which is investigating undercover policing - that intelligence was gathered on her on at least five occasions, between 1998 and 1999.
She told the broadcaster she "felt sick" when she heard the news.
Ricky Reel disappeared during a night out in Kingston on October 15, 1997, shortly after he and his friends were racially abused by a group of white men.
His body was found in the River Thames a week later.
His family and supporters claim he was killed, but Kingston police has always insisted there is no evidence to support the theory.
In 1998, Kingston's then Chief Superintendent Bob Moffat criticised news stories which linked the force's handling of the case to that of murdered teenager Stephen Lawrence.
John Azah, who is chairman of the Kingston Race and Equalities Council and chairman of the Kingston Safer Neighbourhood Board, helped Mrs Reel organise a "Justice for Ricky" campaign in 1998.
He said: "If it is true that the family has been investigated for whatever reason, when all they were trying to do was find out what caused his death, that in my book is beyond the pale.
"I continue to hold the objective view that we may perhaps never know what happened to Ricky, and I have supported our police force and tried to instill public confidence and pride in them.
"But when you find out the police may have investigated a family naturally looking for justice, it doesn't give you much confidence."