Khat fight!

The city’s largest police union is battling an NYPD watchdog group over what constitutes a body cavity search after cops found a man with African drug khat, which can stain a user’s mouth — and ordered him to open up for inspection.

Cops pulled over the 28-year-old driver on McDonald Avenue in Midwood, Brooklyn in October and saw khat, or Bushman’s tea in his car, police sources said.

One officer asked the driver to open his mouth because khat — a plant whose leaves are chewed for its euphoric effects and is illegal — can turn a person’s mouth green or brown. 

When the cops allegedly saw the driver’s tongue was discolored, they arrested him and found $100,000 in suspected drug proceeds in the car, according to the sources. 

The driver, whose name wasn’t released because the case was later sealed, complained about the stop to the Civilian Complaint Review Board, which opened a probe against the cop claiming abuse of authority. 

About 100 investigators — some of whom have been public about their anti-NYPD bias — probe complaints lodged against cops.

Christian Jett, the CCRB investigator assigned to the khat case, labeled the incident “Abuse of Authority: Cavity search,” the PBA told the agency in a letter protesting the description.

The union insists asking a person to open their mouth during an arrest isn’t a body cavity search. The NYPD Patrol Guide doesn’t specify but seems to suggest a body cavity search refers to a person’s private parts.

“If pursuant to a strip search, any object or foreign material is visually detected within any body cavity of the suspect the desk officer will be notified immediately,” the guide says in a section about the searches.

Cops frequently ask suspects to open their mouths to ensure they aren’t holding drugs or weapons, said one recently retired veteran officer, who has 25 years on the job.

“Having someone open their mouth has never been a body cavity search,” the former cop said.

The officer in the khat case could end up with a charge on his public record, stating he performed an illegal body cavity search, which looks bad to future employers, the retired cop said.

“It’s ridiculous because you’re ruining somebody’s career without having the facts,” he said.

The union wrote a letter to the CCRB demanding it retrain or fire Jett for “gross misconduct.”

But the CCRB shot back that Jett didn’t act improperly because the agency has deemed oral searches body cavity searches in the past, an agency spokesman said.

The CCRB has opened probes into “improper body cavity searches of the mouth at least 10 times, substantiating two of those allegations,” CCRB spokesman Dakota Gardner said, adding that one officer was disciplined by the NYPD. He didn’t provide details.

“No single investigator solely determines which allegations to plead and the implication that they do is false and misleading,” he added.

This is the union’s first improper cavity search of the mouth battle — and has been ramping up its fight against the CCRB, suing the group twice in April for releasing disciplinary records and unsubstantiated misconduct claims.

PBA President Patrick Hendry called the CCRB “shameful.”

“We will not allow these cop-haters to retaliate against our members by weaponizing the well-established definition of ‘cavity search,’ he said. “It is clear that this illegitimate ‘agency’ will do anything to destroy police officers’ reputations and lives.”

Jett couldn’t be reached for comment.