The watchdog behind a Twitter account that documents NYPD vehicle-parking abuse, usually with photos, says he was visited by Internal Affairs Bureau cops — but only to threaten him into stopping.

The user, who asked that his name be withheld for fear of police retaliation, said he has been frequently harassed by cops and their affiliates while trying to hold them accountable using the popular handle @placardabuse.

The worst incident, he said, was on Feb. 2 when officers identifying themselves as IAB showed up at his house while he was putting his kid to sleep, quizzed him about the pictures and then discouraged him from keeping tabs on cops.

“It was hostile from the beginning,” he told The Post. “The questions seemed geared toward why I was making a complaint and why I was trying to get the officer jammed up, and not toward anything that would be useful in addressing the misuse of the placard and license-plate covers that were reported.”

The watchdog started the Twitter feed in early 2016 to expose municipal workers who misuse city-issued parking placards — which let drivers ignore certain restrictions if they’re parking in the line of duty.

Ironically, an internal memo that recently went out threatening NYPD cops with enforcement said the placard unit will, in part, be “utilizing Twitter feeds that show violators.”

Police refused to comment unless The Post would reveal the man’s full identity and address.

“Without any information that would enable us to look into these accusations . . . there’s absolutely no way to look into this or find out if it even occurred or is even true,” said department spokesman J. Peter Donald.