Most NYPD brass have no idea why they got promoted — and most who don’t get bumped up don’t know why they were passed over.

Those are the findings from an internal report critical of the police department that lawyer John Scola plans to use in a lawsuit in which four retired Asian captains accuse the NYPD of discrimination when deciding who will join the upper echelons of the nation’s biggest police force.

“The short of it is, it’s too little too late for these guys,” Scola said. “But we hope this lawsuit will drive substantive change moving forward and fix the problem ultimately.”

Scola filed a Brooklyn Supreme Court suit against the NYPD initially on behalf of Ahmad Alli, a retired Asian captain who spent more than 10 years in that rank but was never able to get promoted.

The suit alleges about six out of 10 white captains get promoted beyond the rank of captain compared to about two of 10 Asian captains.

Scola is now hoping for a class action certification for the suit and has added as plaintiffs three more retired Asian captains, each of whom he said “stayed at the captain rank for an inordinate amount of time, based on their skills and knowledge,” even training younger precinct commanders.

“None of our clients want to sue the NYPD,” Scola said. “But they’re doing it in order to drive change.”

Asians of all ranks make up 14% of the entire NYPD force.

NYPD cops take tests to become sergeants, lieutenants and captains. But subsequent boosts in rank, known as discretionary promotions, don’t require tests. They have often been criticized as based on cronyism and patronage — and on race, as the NYPD has strived to diversify its public face.

The report Scola plans to cite in the Asian captains’ lawsuit was authored in 2018 by an NYPD lawyer and three deputy inspectors with the department’s Police Management Institute, which is connected to Columbia University’s executive education programs.

It found that for the years 2015 through 2017, Asians spent on average 7.2 years as captains before getting promoted to deputy inspector — more time than any other minority group.

Black men and women stayed captain for an average of 3.3 and 2.9 years, respectively, while Hispanic men and woman were captain for 3.8 and 5.4 years.

White men spent on average of 6.9 years as captain. White women stayed in that rank for 4.2 years.

The report said the discretionary promotion system lacks structure, guidelines and any form of “mentorship or professional development programs to lay the groundwork for executive professional advancement.”

The most critical problem with promotions beyond captain, the report found, is the “lack of feedback, both to those executives who are successfully promoted and for those who are not.”

Of 213 captains surveyed who had been recommended for promotion, 170 of them, or 80%, did not even know they had been recommended, the report found.

Only six were told by their commander why they weren’t promoted and only 19 got any sort of feedback after their rejection. Most of them, 87%, called the promotion process unfair.

“It’s based on race, gender and relationships,” one captain wrote. “There is no formal mechanism in place for advancement.”

Captains who did become deputy inspectors were also surveyed as part of the study.

Of the 110 who responded to the survey, only 20 said they were fully informed of how the promotions process works, the report said. Ninety-two deputy inspectors, or 84%, called the process unfair.

“They need to be clear and transparent on who will be eligible for promotion and why,” one deputy inspector wrote.

The NYPD, citing pending litigation, refused to answer any questions about the survey, including what changes were made after the study was completed under the leadership of then-Commissioner James O’Neill.

Mayor Bill de Blasio’s administration in 2021 required NYPD brass considering someone for a discretionary promotion to interview at least one person from a demographic considered “underrepresented.”

That idea was based on a rule adopted in 2003 by the National Football League, which is called the Rooney Rule. The rule is named for late Pittsburgh Steelers owner Dan Rooney and requires at least two minorities be interviewed while hiring for certain top coaching positions, including head coach.

Mayor Eric Adams — who in 2021 was Brooklyn Borough President — at the time called the NYPD’s adoption of a modification of the NFL’s idea a “meaningful step” but said more concrete steps needed to be taken.