The report, by the management consulting firm Linder & Associates, painted a picture of a department mired in disorganization and increasingly besieged by 911 calls, some of which never got a response.

"We've not seen this sense of a condition of being overwhelmed in any other major city," said John Linder, president of the consulting firm.

Auditors studied crime reports only from 2002, but shed light on previous years through interviews with more than 200 police officers and a confidential survey to which about two-thirds of officers responded. Atlanta residents were also interviewed and surveyed.

Several police officers told auditors that during the selection process for the 1996 Olympics "a concerted effort" was made to improve Atlanta's chances for selection by underreporting crime to the point of discarding incident reports and improperly closing cases. Their claims have not been verified.

Nearly half the officers who responded to the survey said they believed that crime reports were routinely changed to downgrade incidents. One former deputy chief said that if crime were reported correctly "it would drive the tourists off," Mr. Linder said.

Violent crime that Atlanta reported for F.B.I. national statistics in 2002 was 6.8 percent lower than it should have been, the report found, while the F.B.I.'s margin of error is two percentage points. Reports for 22,000 responses to 911 calls in 2002 cannot be found in department files.

Adding to the problem, the report said, is that the city has 15 law enforcement jurisdictions, like university and public transportation police, which do not send their crime reports to the Atlanta police or the F.B.I.

The study was commissioned by the Atlanta Police Foundation, a group of business leaders that raises money to support police efforts, at the request of Chief Richard J. Pennington. Elizabeth Kelly, the foundation's director, said the chief asked for the audit after he came to Atlanta in 2002 so he could develop an action plan.

Chief Pennington said in a statement yesterday that the department would use the report to revamp its operations, including asking for more officers and pay increases -- 92 percent of officers said they felt they had to work extra jobs to support their families -- and establishing an audit unit.