Yesterday, the Independent Police Complaints Commission published an investigation into allegations in The Independent earlier this year that a key investigator in the first, botched hunt for the killers of Stephen Lawrence was engaged in extensive criminal enterprises.

The story was based on unpublished Metropolitan Police files. The implications could not be more far-reaching: such corruption could have hampered the original inquiry into a murder which was a watershed in Britain's race relations.

The IPCC has been unable to find any new evidence on either our allegations, or others which followed in another newspaper. But the police watchdog's report is a flawed piece of work that makes an erroneous – and highly prejudicial – assertion that we cannot allow to pass unchallenged.

An IPCC official approached The Independent with questions about our initial article and was directed towards its co-authors, the two investigative journalists, Michael Gillard and Laurie Flynn, who have written a book on corruption in the Metropolitan Police based on more than 1,000 interviews with lawyers, whistle-blowing detectives and police supergrasses.

Not only did the IPCC make no attempt to contact either the editor or the news editor of this newspaper. It has also included in its report the startlingly disingenuous claim that The Independent's reporter confirmed that he had "no evidence" to substantiate the story about the Lawrence case. This is both untrue in itself and a gross misrepresentation of what was said, which went no further than the suggestion that the IPCC contacted Mr Gillard.

This newspaper is not in the business of printing stories without the evidence to back them up, particularly on so delicate a subject as the murder of Stephen Lawrence. It is impossible not to conclude that the IPCC has published its report prematurely, without fully completing the necessary inquiries. Public confidence in the police, and its watchdog, requires a more thorough investigation of allegations of serious corruption within the capital's force. And we require a retraction of the slurs on our journalism.