The public inquiry announced today will examine the Special Demonstration Squad, the Metropolitan Police's undercover unit.
It was set up in the 1960s to infiltrate protest groups. One former member has claimed he had been told to find information to smear the Lawrence family.
ITV News correspondent Paul Davies has been looking into the background of the secret squad:
A senior Met Police officer has been moved from his role following the publication of a report into Stephen Lawrence's murder investigation.
Almost 21 years after Stephen Lawrence was stabbed to death, the Home Secretary has ordered a public inquiry into undercover policing .