A new NYPD directive forbids cops from entering a residence in response to a noise complaint — unless they’re given permission.

The directive, a copy of which has been obtained by The Post, means loud partiers can simply tell the cops who come to their door to just go away.

The bizarre constraint is the result of costly, successful lawsuits against the city by homeowners who complained that cops barged onto their properties without a warrant, multiple sources told The Post.

A week after it was issued, the directive had already outraged brass and rank-and-file cops alike, who warned Wednesday that neighborhoods will suffer from sleepless nights and trash, and that the NYPD will lose the vital ability to police out-of-control parties by known or suspected gang members.

“This might be the dumbest thing I ever heard in 20 years policing,” one law enforcement veteran told The Post.

“This is very bad for all,” complained another law enforcement source.

“More people will be shot and assaulted, neighbors will lose sleep, and garbage will be strewn all about. This is our new progressive city.”

Noted another law enforcement source, “I guess they’re sick and tired of getting sued so often … People were going to jail, sound systems were being broken or confiscated, and then the judges throw the cases out. I think they’ve had enough lawsuits.”

Cops had confiscated so much sound equipment last year that an NYPD warehouse “looked like PC Richards,” quipped another source.

The directive, issued to all NYPD commands, instructs that cops can no longer go inside a home without consent “solely for the purpose of abating noise conditions by enforcement action and/or seizure of the device,” the directive reads.

“Members are advised that in cases where an unreasonable noise condition exists on private property and the owner/custodian of the premise refuses to cease the noise, members may return on the following day and issue summonses as appropriate,” the directive reads.

“Parties will go into early morning, which will involve more drinking and neighbors getting into fights, resulting in more shootings,” noted another law enforcement source.

“It will be a long, hot summer.”

The directive essentially contradicts their own Patrol Guide, which allows them to forcibly enter a residence or club if the noisy partiers inside have ignored warnings to turn the volume down.

In those cases, “the decision to forcibly enter into private or semi-private premises to correct noise complaints will ONLY be made by a precinct commander/duty captain and ONLY as a last resort, after requests to stop the noise have been ignored,” the Patrol Guide instructs.

In superceding the Patrol Guide, the new, “no consent, no entry” directive takes away that commonly resorted-to “last resort,” cops complain.

Asked about the directive, a police spokesman insisted to The Post Wednesday that “We spoke to legal. Nothing has changed.”

But the spokesman declined to immediately produce a previous directive, from any past year, telling cops to ignore that section of the Patrol Guide.

“They’re trying to protect themselves from more lawsuits by saying this has always been the case,” one law enforcement source told The Post.

“They don’t want new people coming forward and saying, ‘I had a party last year that cops busted up'” and then suing the city.

He stressed, “It’s new. That’s not what we’ve always done. That’s why they came out this bulls—” directive, he said. “This is total horses—.

“The department should just own up to it.”