Mayor de Blasio on Friday refused to stay the execution of a deer that wandered into Manhattan — saying it would be more humane to kill it because relocation would lead to a long, traumatizing death.

“There’s no other option,” the mayor insisted on WNYC radio, rejecting Gov. Cuomo’s offer to try to safely relocate the deer.

The deer isn’t injured, but de Blasio said the process of moving it would be too “traumatizing” and lead to “all sorts of extended pain” because the deer wouldn’t be able to adapt to a new environment.

But animal-rights lovers — and even one of his own former key campaign aides — were quick to blast the mayor.

“De Blasio has a long history of murdering animals. #chuck #neverforget,” tweeted Lis Smith, referring to the ham-handed mayor’s famous fumble of Staten Island Chuck, the weather-predicting groundhog who died after de Blasio dropped him.

Smith was de Blasio’s campaign spokeswoman but resigned after it surfaced that she was romantically involved with disgraced former Gov. Eliot Spitzer.

An animal-rights activist was crying over the fate of the deer outside the city’s ASPCA headquarters in East Harlem on Friday morning.

“I’m an animal lover. It should be released or put in Central Park Zoo. It’s wrong, they wouldn’t want to be put down themselves,” Carolyn Andino, 48, told The Post.

I love Gov. Cuomo, he’s got spunk,” Andino said. “I wish Obama would get involved, he wouldn’t let it happen.”

The comments come as a rep for the mayor said the “state directed the city to either release the deer in Manhattan or euthanize it. Releasing the deer in the Manhattan is clearly not safe.

“[T]he only humane and safe recourse is to euthanize the deer, and that will happen in the morning,” the mayor’s rep said, adding that releasing the buck back into the wild is “not safe.”

The governor’s office disagreed, insisting there are “alternatives to euthanasia…including relocation.”

Smith, who famously dated, then dumped former governor Eliot Spitzer, heaped praised on Cuomo’s life-saving efforts.

“It’s not a joke. Why in the world would anyone kill a deer missing an antler? Good on Cuomo.”

“Seriously, what is wrong with these people. Jesus, let Cuomo take the wheel on this and homelessness.”