A HOME Office report into Operation Lancet has criticised the investigation for being poorly managed.
The Government's investigation into the corruption inquiry, which centred on Cleveland Police, was launched in April.
It has criticised Lancet for not acting quickly enough and for putting too much pressure on some investigators.
It pointed out that, with a final bill to the taxpayer of £3.2m, the investigation ran up "apparently unconstrained expenditure".
A breakdown of costs in the report also revealed that West Yorkshire Police, who were brought in to assist the Lancet team, ran up a bill of more than £700,000 since 1999.
Ashok Kumar, MP for South Middlesbrough and East Cleveland, said the report vindicated his belief that the inquiry had been a waste of time and taxpayers' money.
After making it clear he had not read the full report, he said: "It is clear that this was a sledgehammer to crack a walnut.
"I still think there needs to be an honest examination by HM Inspectorate of Police into how much taxpayers' money has been spent on Lancet in Cleveland."
The report revealed that nearly £900,000 in salaries and £430,000 in overtime was paid out during the four-year inquiry.
It said Lancet put "unnecessary and debilitating pressures on individuals involved" and the "investigatarory activity was disproportionate to the central issues".
The report concluded: "This cocktail, rather than resulting in effectiveness, which must be the outcome that best represents the public interest, can be a major contributory factor in creating widespread dissatisfaction."
Recommendations in the report included streamlining the way complaints are investigated and better methods for choosing senior investigators.
It also recommended a joint training and performance monitoring system between police, the Crown Prosecution Service and the Police Complaints Authority.
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