Lawrence: Did detective tip off suspect's family?

A detective at the heart of the botched first inquiry into the racist murder of Stephen Lawrence in 1993 is likely to be investigated for corruption after an allegation that he was being paid by the criminal father of one of the five prime suspects.

John Davidson, a detective sergeant in the Metropolitan Police, is claimed to have told a colleague he was "looking after" David Norris, one of five men arrested after the killing and the son of Clifford Norris, a south London gangster.

The Independent Police Complaints Commission said last night that it expects Scotland Yard to refer the allegation - made in a BBC documentary to be screened tonight - to its investigators to launch a full-scale inquiry.

Neil Putnam, a former detective who served with Mr Davidson and was himself found guilty of corruption, claims that when he told the Yard of his colleague's relationship with Norris the allegation was covered up.

In a statement, the IPCC said: "There are two serious allegations in this film and we will be asking the Metropolitan Police Service to record the misconduct complaints. We would then expect the MPS to refer them back to the IPCC."

The police inquiry in the hours and days after the stabbing of Stephen Lawrence, 18, an A-level student, in Eltham, south-east London, was beset with errors and incompetence which meant that vital forensic evidence was missed or lost.

The Macpherson report into the killing said the inquiry was "marred by a combination of professional incompetence, institutional racism and a failure of leadership by senior officers".

Although members of the inquiry have stated there was a "whiff" of corruption about aspects of the investigation, the report found that the suspicions, shared by Stephen's parents, Doreen and Neville Lawrence, were unproven.

But the documentary, The Boys Who Killed Stephen Lawrence, made by Mark Daly, the reporter whose award-winning film, The Secret Policeman, uncovered racism among trainee officers in Manchester, brings to light claims of collusion. After Stephen was killed, five suspects - Neil and Jamie Acourt, Luke Knight, Gary Dobson and Norris - were charged with murder. Neil Acourt, Dobson and Knight were acquitted when a private prosecution brought by the Lawrence family was thrown out of court. The case against Jamie Acourt and Norris was dropped before it reached court. No one has been successfully prosecuted for Stephen's murder despite three police investigations, including a £4m reinvestigation led by John Grieve, the former head of the anti-terrorist branch.

Supporters of the Lawrence family have long voiced concerns that the suspects appeared to stay one step ahead of the initial police investigation. Jamie Acourt was able to emerge from his home five days after the murder carrying a black binliner without being stopped or followed by a police surveillance team. Neil Putnam, who was not involved in the Lawrence case but knew Mr Davidson when he joined another Yard unit, said he had on one occasion been passed a envelope by his colleague containing £500. Mr Putnam, who was jailed for corruption in 1999 along with five other officers, claimed Mr Davidson, who has now retired and runs a bar in Minorca, had revealed to him his relationship with Clifford Norris, a wanted drug smuggler. Mr Putnam told the BBC: "Davidson told me that he was looking after Norris and that to me meant that he was protecting him, protecting his family against arrest and any conviction." He added: "From my conversation ... with John Davidson on that day, I would say that [he] was receiving cash from Clifford Norris."

It is understood that the allegation made against Mr Davidson is that he was being paid for information about the progress of the investigation. When approached by the documentary team, the retired officer denied Mr Putnam's claims and any wrongdoing.

Deputy Assistant Commissioner John Yates, who is in charge of crime reinvestigation, told the programme: "From all the evidence I have seen ... I have no doubt Mr Davidson was corrupt."

Mr Davidson is the second officer involved in the Lawrence inquiry alleged to have had a relationship with Clifford Norris. The Macpherson Inquiry heard that David Coles was seen meeting the gangster in the late 1980s and receiving a carrier bag containing unknown items.

Imran Khan, the solicitor for Doreen Lawrence, said there were "serious indicators" of corruption and called for a full investigation.