Report on police corruption, which questioned commander's conduct, was not given to Stephen Lawrence inquiry

Scotland Yard says it is considering keeping secret a report detailing questions about the conduct and integrity of a police chief who went on to be hired by part of Rupert Murdoch's News Corporation.

Former Scotland Yard commander Ray Adams was head of UK security for the software company NDS, owned by News Corp, which allegedly cracked the smartcard codes of rival company ONdigital. The codes then appeared on a pirate website. NDS denies any wrongdoing.

As well as the allegations about NDS, Adams's career is at the centre of demands for a new inquiry into whether the killers of Stephen Lawrence were shielded by police corruption in 1993.

Adams was questioned about corruption during the 1998 Macpherson inquiry into Lawrence's death. But neither the Lawrence family nor the inquiry panel were given a report by Scotland Yard containing the findings of an investigation by its anti-corruption command.

The Met's investigation into Adams began in April 1987, by which time he had risen to become the Met's head of criminal intelligence, in charge of gathering information about major criminals and criminal networks. The investigation, codenamed Operation Russell, raised questions about Adams's conduct in the years before the Lawrence case. Adams insists the report exonerates him and told the Guardian he denies any wrongdoing.

The Guardian has formally sought the release of the Operation Russell report under freedom of information legislation. But the Met says it may seek to keep the report secret using an exemption.

In response to the application, the Met said: "We are currently considering whether 'qualified exemptions' apply to the information you have requested."

The Met said the exemption it was considering invoking covered "investigations and proceedings conducted by public authorities". It said it would make a decision by mid-May.

Stephen's mother, Doreen, and the Labour party have called for a fresh public inquiry into the allegations about possible police corruption. The home secretary is treating the allegations as of the "utmost importance".

Operation Russell ended with no criminal or misconduct charges being brought against Adams but listed concerns about him, in one instance describing his conduct as highly questionable and unprofessional.

The investigation was carried out by the Met's complaints investigation bureau and was triggered by allegations that Adams had taken bribes from criminals and had improper relationships with criminal informants, which he strenuously denied.

Keith Vaz MP, chairman of the home affairs select committee, said: "Nineteen years after Stephen Lawrence's murder, the handling of the original investigation by the Metropolitan police remains in the spotlight. I am very concerned that the Metropolitan police appear to be preventing the findings of Operation Russell from being made public. In order to give complete closure to the Lawrence family and to reassure the public there must be complete transparency."

Guidance from the information commissioner says: "The information can only be withheld if the public interest in maintaining the exemption outweighs the public interest in disclosure. This involves weighing the prejudice that may be caused to an investigation or prosecution, or more generally to the investigatory and prosecution processes of the public authority, against the public interest in disclosure."

Some of the allegations against Adams centred on his relationship with the subsequently convicted murderer Kenneth Noye.

After retiring from the Met in 1993 for medical reasons, Adams was hired by Murdoch's NDS. A BBC Panorama programme last month alleged that NDS used computer hacking to undermine the business of its chief TV rival in Britain.

Based on witness testimony and emails, the BBC programme alleged that NDS cracked ONdigital's smartcard codes. ONdigital eventually ceased trading amid a wave of counterfeiting by pirates, leaving the lucrative pay-TV field clear for Sky.

According to the BBC, the codes were passed to Adams as head of UK security for NDS, which made smartcards for Sky. NDS was jointly funded by Sky, which says it never ran NDS.

It is alleged that once ONdigital's codes were cracked by NDS, they were subsequently publicised on the pirate website The House of Ill Compute, or THOIC.

Lee Gibling, operator of THOIC, has alleged that behind the scenes he was being paid up to £60,000 a year by Adams, and NDS handed over thousands more to supply him with computer equipment.

He said Adams sent him the ONdigital codes so that other pirates could use them to manufacture thousands of counterfeit smartcards, giving viewers illicit free access to ONdigital, which was then locked in fierce competition with Sky.

The company does not dispute the allegations that it got its hands on ONdigital's secret codes, which was not itself illegal, and that the material was passed on to Adams, its security chief. But NDS says there is an innocent explanation "as part of the fight against pay-TV piracy".

The company added: "NDS has never authorised or condoned the posting of any code belonging to any competitor on any website." Adams has denied he ever had the codes.

Clive Efford, the Labour MP for Eltham in south London, where Stephen Lawrence was murdered in 1993, said the Met should release the Operation Russell report and not try to invoke an exemption: "There is no justification for this report being kept secret. It's not acceptable."

Efford said the report should be released "if we are going to satisfy the public that justice has not been interfered with".

Adams told the Guardian in March that Operation Russell and the Macpherson inquiry had both exonerated him. Of the Met investigation he said: "The head of the investigation shook my hand at the end of it and said 'You are the only person who's probably told the whole truth'."