Mayor de Blasio on Friday defended the hiring of his wife’s chief of staff, Rachel Noerdlinger, despite her long live-in relationship with convicted killer and cop-hater Hassaun McFarlane.

“I have full faith in Rachel,” de Blasio said on Friday at City Hall.

“You don’t fire people because of something their boyfriend said. That’s ludicrous.

“I have absolute faith in her and I know what I value and she values the same thing.”

McFarlane, who has been Noerdlinger’s beau for six years, has a long criminal history. He pleaded guilty to manslaughter for shooting an 18-year-old rival over a down jacket when he was 15, an official source confirmed.

He was sentenced to four years in prison on interstate cocaine trafficking charges in Bristol County, Mass., and was released in 2007.

McFarlane was charged with marijuana possession in 2012 and spent seven days in jail in 2011 for driving with a suspended license, records state.

His most recent brush with the law was last November, when he pleaded guilty to disorderly conduct, after he was accused of running a cop off the road in Edgewater, NJ,. with Noerdlinger’s Mercedes.

McFarlane, 36, also has made his hatred for cops clear, calling them “pigs” on Facebook many times.

PBA President Patrick Lynch called for Noerd­linger’s firing, out of “serious concern” the information that she hears at high-level NYPD CompStat sessions could be passed along to a hardened felon.

But de Blasio stood by Noerdlinger, 43, a former press aide to the Rev. Al Sharpton who makes $170,000 as First Lady Chirlane McCray’s top adviser. He swatted away questions over whether he should dismiss her as guilt by association.

“Respectfully, I think the question you’re asking is the wrong question. We don’t care what someone’s boyfriend said, we care what the public servant’s about,” he said.

“She’s very dedicated to the work of bringing police and community together and that’s what we care about.”

Some political insiders see a double standard.

Last year, during his transition period, de Blasio canned Lis Smith as his spokeswoman after The Post revealed she was dating the still-married and disgraced ex-Gov. Eliot Spitzer.

McFarlane’s criminal history was not news to the mayor and McCray, according to a City Hall aide.

“Rachel was very candid from the beginning,” the aide said.

Additional reporting by Kathleen Cullitonand Aaron Feis