Oakland’s former police chief tried for six months to muzzle allegations that multiple officers sexually exploited an underage girl, and encouraged his department to drop its internal probe of the misconduct, according to a report released Wednesday by a court-appointed monitor.

The report, commissioned by U.S. District Judge Thelton Henderson, placed the bulk of the blame on former Police Chief Sean Whent and the scornful attitude he fostered toward certain police victims.

“Chief Whent sent an unmistakable signal that this case was not a priority,” investigators Edward Swanson and Audrey Barron wrote in the 33-pagereport. “This is perhaps not an isolated occurrence, since witnesses from within and outside the department described a hierarchy of victimhood that led some in OPD to prioritize cases involving ‘good’ victims over victims with more complex histories. …

“She was a young woman who was alleged to have had repeated sexual contact with law enforcement officers — officers who took advantage of her age and vulnerability. Given the allegation that she had been sexually exploited by OPD officers, OPD owed her at least the same patience, concern, and investigative attention that they afford other victims. Put simply, CID [Criminal Investigation Division]and AID [Internal Affairs Division] wrote off this victim.”

Allegations that a slew of officers from law enforcement agencies around the Bay Area had sex with the teenage daughter of an Oakland police dispatcher came to light in September 2015 after Oakland police Officer Brendan O’Brien killed himself and left a suicide note implicating several other Oakland officers.

O’Brien took his life partly because he feared what the girl, who went by the name Celeste Guap, would expose about him, according to the report.

But Whent did not tell Oakland Mayor Libby Schaaf or a federal monitor overseeing police department reforms about the allegations in O’Brien’s suicide note. Instead, the allegations were passed on to the criminal investigation and internal affairs divisions, whose investigators conducted “deficient” and “defective” inquiries on which Whent failed to follow up.

“He did nothing to ensure the allegations were being investigated appropriately,” the report states.

According to the report, the CID probe consisted simply of interviewing Guap and reviewing evidence on O’Brien’s phone, and was closed within a week, with investigators concluding that no crime had occurred.

The CID punted the inquiry to internal affairs, which appointed just one investigator, who never interviewed Guap in person, ignored key leads and recommended discipline for a single officer.

Although 12 Oakland officers were eventually disciplined and six charged with crimes involving Guap, ranging from oral copulation with a minor to obstruction of justice, Swanson and Barron slammed the Oakland Police Department for failing to conduct a serious investigation until Judge Henderson intervened.

Citing “irregularities and potential violations” of a negotiated settlement agreement that requires OPD to coordinate with the district attorney’s office on potential officer criminal misconduct that occurred during IAD investigation, Judge Henderson turned the investigation over to the federal monitor in March 2016, the same month “when the monitoring team learned, almost by accident and not from the chief, about the investigation,” Swanson and Barron wrote.

“OPD’s initial investigation of this case – both as a criminal matter and as an internal affairs matter – was seriously deficient,” the monitors wrote. “If not for the court’s intervention, we have no confidence that correct discipline would have ever been imposed, criminal charges filed, or departmental shortcomings examined.”

Henderson appointed Swanson and Barron after Mayor Schaaf’s outside investigator failed to issue any findings on why internal affairs failed to adequately investigate the case.

Although Schaaf and other city leaders “were actively involved” in overseeing the police departments own investigation after they learned about the allegations, Swanson and Barron found that they failed to press their investigator for answers after “many months” of stalled progress.

“I accept that criticism,” Schaaf said at a news conference Wednesday. She added: “Those months we were very focused on the Ghost Ship fire recovery, as well as onboarding the new police chief, who is the most important part of addressing the concerns raised in this report.”

Oakland settled a legal claim with Guap in May for nearly $1 million. Her attorney, John Burris, could not be reached for comment late Wednesday.

Oakland Police Chief Anne Kirkpatrick, who was hired in January after Whent and two other interim chiefs resigned during public revelations of the scandal, acknowledged the poor treatment some victims receive from OPD and vowed to root it out.

“This is all about course correction,” Kirkpatrick said at the news conference. “One of the commitments I can make to you is how we treat our victims with new eyes and with care and attention. And that is what we are going to do.”