OAKLAND — Police overtime — a sore subject that has dogged the city for well over a decade — costs Oakland about $30 million a year, according to a new city audit.

More than 200 officers each worked at least 520 hours of overtime last fiscal year, according to a separate report by financial consulting firm Harvey M. Rose Associates. One clocked more than 2,600 hours in a year and another earned $104,588 in overtime last year.

A report released Monday by City Auditor Courtney Ruby analyzed the Police Department’s overtime practices over the last four fiscal years and concluded the city needs to “take significant steps” to better manage overtime and increase transparency on the true costs of overtime.” The city exceeded its overtime budget by an average of $13.7 million each year, the report says, and needs to be more “realistic” with its overtime budget projections. Much of the deficit is offset by cost savings from vacant positions and reimbursement for overtime spent by officers patrolling special events.

“Ultimately, other city priorities suffer when the [police] department’s deficits must be covered,” Ruby said in a letter to city officials attached to the report.

The City Council is in the middle of its budget review for the next two fiscal years and must adopt a final document by the end of the month. The administration’s budget proposal only calls for around $15 million each year to be spent on police overtime.

Excessive police overtime has been on the city’s radar at least since Jerry Brown was mayor from 1999 through 2007. At the time, police officials blamed the “culture of overtime” on officers filling in for the dozens who had been laid off.

During a review of police overtime practices in 2015, the city auditor found that such costs had “skyrocketed” from the year before. Again, the reason cited was that officers had to fill in for departed cops.

Since then, the department has hired 87 officers and no longer requires them to work regular mandatory overtime, according to the recent report. That resulted in a 20 percent drop in overtime hours from the 2014-15 fiscal year to the 2017-18 fiscal year, the report said. Since personnel costs have increased, the drop in hours didn’t result in a drop in costs, according to the report.

But officers are still working what Ruby considers an “unsafe” number of voluntary overtime hours, which could lead to “significant health and safety consequences for our officers and our community.” Auditors found that three officers worked more than 70 days in a row and some worked overtime while on paid leave.

The department has not done enough to document the authorization and approval of overtime, the report says, and needs to crack down on officers working “excessive” overtime hours. The audit mentions that the officer responsible for scheduling officers to staff events consistently assigns himself to also work those events, and is in turn the second highest overtime earner over the past five fiscal years.

Police management agrees with the recommendation and is working to implement a new, more stringent overtime policy, according to the department’s response to the report. That policy will be implemented by 2020.