Off-duty cops who plan to see the pope during his tour of the Big Apple ​are being warned to leave their guns at home — or face being ​sent away and ​reprimanded by NYPD brass, police officials warned in a memo.

“All members of the service who plan to attend a papal event while off-duty are hereby advised that firearms will not be permitted,” read a message sent to police officers on Wednesday.

“Any member with a firearm will be excluded from the event.”

Despite ​heightened concerns about an assassination ​​attempt​ or act of terror​, off-duty cops will ultimately have to abide by the very same rules that civilians are asked to — a move that is not sitting well with members of the force.

“This is our city and we should be able to carry,” a police source said, describing the policy as “very offensive.”

“God forbid something happens,” he explained. “You’re going against the patrol guide which says you’re required to be armed at all times while in New York City. ​If​ something bad happens and you’re not armed, you’re not able to protect yourself, your family, friends and the public. You have the leader of the biggest religion in the world and the potential for violence is there. I’d like to be able to protect myself if something, God forbid, does happen.”

Another source added, “​I​​n cases like this, it’s always better to have your gun and not need it, than to not have your gun and need it. Obviously, in the case of the pope, we’re all worried about an assassination attempt.

​”​It would be better to have a professional NYPD cop with his sidearm because that adds another layer of security for the pope. We want to protect him in every shape or form. If a cop is walking to one of the vents and sees something and needs to engage with his weapon, you’re going to want that gun on you.”

Ed Mullins, president of the Sergeants Benevolent Association, also blasted the no-gun protocol — calling it “insulting to all members of the NYPD.”

“This makes no sense,” he said. “The NYPD has stated the Papal Detail is a high-risk security event and then prohibits the very same members of the NYPD from carrying their department-issued firearms off duty while attending a papal event with their families. I guess someone forgot law enforcement members are being targeted and killed across the nation.”

In addition, police sources referred to the requirement as “another slap across the face to the police department, where our leader does not back us.”

“It shows that Commissioner Bratton bows down to whatever he’s told to do,” a police source said. “Bratton should have backed us, said these are my cops, if they want to go, they should not be denied entry. This is just more security and eyes that would be out there to possibly thwart anything that might happen.”