Mayor Bill de Blasio created a $150,000-a-year job to boost his national immigration agenda — and then the cushy position was handed to the live-in girlfriend of one of his most trusted aides, The Post has learned.

Stephanie Yazgi, 38, the longtime partner of senior mayoral aide Emma Wolfe, 35, was hired in May for the unadvertised position of “campaign director” in the mayor’s Office of Immigrant Affairs.

“That’s just a made-up position,” said one Democratic insider. “It makes no sense. They create a position for her for $150,000 that’s a redundancy.”

Yazgi will be responsible for “overseeing the mayor’s national organizing efforts on immigration, specifically the Cities for Action on Immigration coalition,” according to a job description provided by City Hall.

The position was initially to be funded by a private grant, but because of “delays,” taxpayers will be footing the bill instead.

Immigration Commissioner Nisha Agarwal said she recruited Yazgi because she headed a list of “about 10 people who were my top job choices.”

But City Hall officials refused to say if anyone else was actually interviewed.

While Agarwal insisted Yazgi is “very experienced” in the field of organizing, with 15 years of experience, another Democratic insider questioned her qualifications. “I can’t think of anything — and I’ve worked with her — that gave her experience on that level,” the source said. “Her experience is more labor-oriented.”

A few months before Yazgi was hired, mayoral aides asked for approval from the Conflicts of Interest Board, noting Yazgi “may work on occasion” with Wolfe, her partner. The board determined that since Yazgi would be reporting to Agarwal, the hire would not violate city rules.

“In the board’s view, however, such a periodic working relationship would not render Ms. Wolfe the superior of Ms. Yazgi,” the entire five-member board wrote in a March 6 opinion.

A subsequent letter from the mayor’s immigration office, dated May 15, said Yazgi would also be working “to support coordination of national efforts on inequality more broadly.” The board still decided that was “not in violation” of the City Charter.

Agarwal defended the hiring as a necessary follow-up to the immigration summit de Blasio convened at Gracie Mansion last December with US mayors to promote reforms. “We really needed somebody to coordinate that work,” said Agarwal.

Yazgi has worked at the liberal-leaning Center for Popular Democracy — where she was also hired by Agarwal — and served as the secretary of UPKNYC, the nonprofit “grassroots campaign” that pushed de Blasio’s universal pre-K plan.

To take the new job, she left a community organizer post at Hilltop Public Solutions, the consulting firm that handled de Blasio’s mayoral campaign.

Yazgi shares a Brooklyn apartment with Wolfe.

When asked if Yazgi’s relationship with Wolfe was a concern, Agarwal said, “not really.”

“Stephanie is a veteran organizer, and her skills have helped keep Cities United for Immigration Action growing,” said de Blasio spokesperson Karen Hinton.

Additional reporting by Lorena Mongelli