The Prime Minister says he wants investigations to "get the full truth out" about "horrific" allegations, that police tried to smear the family of Stephen Lawrence.
An undercover police officer claims he was ordered to find information to discredit the family, Duwayne Brooks and campaigners.
He said it happened in 1993, just months after Stephen was murdered at a bus-stop in Eltham in an unprovoked racist attack.
Both the Home Secretary Theresa May and Mayor Boris Johnson spoke about possible criminal prosecutions of Met officers, if the claims prove to be true.
We have this report from our Senior Correspondent Ronke Phillips.
More top news
Police have released CCTV images of a car they want to find in connection to a fatal hit-and-run on Saturday morning.
The family of murdered teenager Jimmy Mizen have held a community event in his memory to raise money for the foundation in his name.
A drawing made for one of the famous paintings from the Victorian era - Flaming June - has been rediscovered after more than 100 years.