An independent police force will review the Metropolitan police’s handling of new evidence relating to the murder of Stephen Lawrence 30 years after his death, the mayor of London has said.

It comes after the Met commissioner, Mark Rowley, apologised to Stephen’s mother, Doreen Lawrence, for not fulfilling a promise to answer questions stemming from a BBC investigation into the murder of the 18-year-old in 1993.

The mayor of London, Sadiq Khan, told BBC News that the Lawrence family had been “let down” by the police and that Rowley would be asking a separate force to review the Met’s handling of “fresh evidence”.

The BBC said Lady Lawrence was promised an explanation after the broadcaster named Matthew White as the sixth suspect in the case last year.

Stephen Lawrence was murdered by a gang of racists in Eltham, south-east London, in April 1993 as he ran to catch a bus with his friend Duwayne Brooks.

Only two of his killers – Gary Dobson and David Norris – have ever been brought to justice.

Asked whether he had confidence in the Met to deal with the case, Khan said: “I think the family has been let down over the last three decades by police officers.

“Dame Louise Casey in a recent report found that the police service was still institutionally racist. I think there are lessons to be learned.

“I had a frank conversation with Sir Mark Rowley today. He’ll be asking a separate police force to look into the assessment that the Met police have made in relation to the fresh evidence.

“I’m hoping that reassures the Lawrence family, Doreen in particular, that under the new leadership in the Met police service, they will redouble their efforts to make sure that Doreen and the family think that this police service has learned the lessons from yesteryear.”

A spokesperson for the Met said: “While we have not identified any additional viable lines of inquiry, recognising the concerns held by Baroness Lawrence and the significance of this investigation we will be asking an outside force to review our approach.”

The original investigation into Stephen’s death was hampered by institutional racism in the Met, and claims that corrupt officers had sought to protect Norris, whose father, Clifford Norris, was a notorious drug dealer.

Last June, the BBC named White, who died aged 50 in 2021, and outlined the bungled handling of evidence against him.

Two witnesses said White had confessed to being present during the attack and one, his stepfather, was not spoken to by police until 20 years after the murder because officers had previously misidentified him.

White was arrested twice in connection with the murder but on both occasions there was not enough evidence for a prosecution, the Met said.

Rowley said: “We recognise this is a particularly difficult time for the Lawrence family and Duwayne Brooks. I am sorry our failure to respond in a timely fashion has added to this.

“On top of the failures over the decades, this is totally unacceptable.

“Restoring trust in the Met is one of my top priorities and that includes how we work with those affected by the failures of the past.

“I apologise to Baroness Lawrence who must have answers to all her questions. I have written to her and offered to meet.”