Damilola Taylor's father has branded the police "clumsy" over their handling of the investigation into his son's murder. Richard Taylor said that police had all the evidence they needed to secure convictions, but failed to present it properly during the Old Bailey trial of four teenagers accused of killing Damilola.

His comments come on the eve of publication of the results of a high-profile inquiry into the case. The report is expected to highlight failings on the part of the Metropolitan Police, which conducted the investigation into the 10-year-old's murder.

"The evidence was all there but it was the way they handled it, they made it become clumsy," he told The Independent on Sunday, adding: "Dealing with witnesses could also have been better done."

The Bishop of Birmingham, the Right Rev John Sentamu, who was a member of the Stephen Lawrence inquiry, will tomorrow publish his report, which was commissioned by Sir John Stevens, the Met commissioner.

The report is not expected to criticise the investigation itself but instead to question the way officers presented evidence during the trial and how they failed to prepare key witnesses properly.

Damilola was found bleeding to death in the stairwell of a block of flats in Peckham, South London, in November 2000. Four teenagers were cleared of his murder earlier this year, in a trial costing £3.5m. Since the trial, the Government has introduced new laws to reform the criminal justice system, including double jeopardy – the ability to try people again for an offence for which they have already been prosecuted.

Mr Taylor, who has not seen the bishop's report, said he hoped these changes in the legal system would enable his son's killers to be brought to justice.

"We still have confidence that justice will be done and hope this law will be put in place," he said. "I'm a law abiding citizen and I've got great confidence in the British legal system. My son's death was not an accident."

He said that he was still traumatised by the defence's suggestion that his son's death had been an accident.

"They came up with incredible stories of an accident, which was an incredible blow to this family. Even now, I can't get over it."

The Metropolitan Police faced intense public and political pressure to catch Damilola's killers and to show they had learnt lessons from the Stephen Lawrence inquiry.

Sir Herman Ouseley, the former head of the Commission for Racial Equality, said police had made every effort to ensure they won the support of the community in Peckham by drafting in black officers. But he said the Met's desperation to secure a conviction and their "overzealous" approach led to mistakes.

"The question is one of competence," he said. "It was obvious the main witness was erratic and was taking the police for a ride."

The key witness in the murder trial was a 14-year-old girl. The jury was played a tape of her singing "I'm in the money", in reference to a £50,000 reward offered by a newspaper in return for information about the murder.

A senior source at the Met said that murder squads were severely overstretched at the time of the schoolboy's murder and that issues such as the handling of witnesses were already being addressed.

"There was also an issue around vulnerable witnesses," he added, "and, at the end of the day, a conviction was not secured, but there was a lot of good work done in liaising directly with the community."