Comptroller Scott Stringer said Friday he plans to take a deep dive into the finances of first lady Chirlane McCray’s “Thrive” mental health initiative following reports that it spent $850 million over four years but has yet to report results.

“I’ve had concerns about the lack of transparency in the Thrive program. This morning I sent a letter to Mayor de Blasio asking for a trove of information raising concerns about the program and whether, in fact, we are seeing results for the $850 million,” Stringer said at an unrelated press conference in his Manhattan office.

“We are taking a step today calling on the mayor to provide our office with the information we need to do a proper analysis.”

Stringer’s letter seeks updates on the 54 health-related programs that Thrive NYC says it oversees, as well as which city agencies oversee each of them and how they’ve “evolved” since the initiative’s 2015 launch.

The letter also asks for the “metrics” City Hall is using to measure the program’s success, how many New Yorkers have sought and received assistance and a “list of community partners” that received city funds through Thrive.

“I want to obviously support a program that is geared to help struggling New Yorkers, people with mental illness,” Stringer told reporters.

“It is a very ambitious program. It’s a worthy program, … but it is time to raise issues of transparency and also accountability.”

The comptroller is also seeking a detailed accounting of Thrive NYC’s distribution of Naloxone kits to local hospitals, including how manywere used and whether they provided “any impact” in preventing opioid overdoses.

Stringer also claims Thrive NYC’s “existing budget codes … appear inadequate to fully track spending.” He is seeking “necessary information” so he can “accurately track” Thrive’s spending — including total state and federal dollars allocated to the program yearly.

His comments came the same day Post columnist Bob McManus questioned why Stringer hasn’t provided more oversight over the costly program.

McCray on Friday fired back at Stringer, saying in a statement she “welcomes [his] ‘hard look’ at Thrive NYC” and “encourage[s] to him and other elected officials to “take our Mental Health First Aid course and … learn more about this area of health that has been so sorely neglected.”

“Perhaps now we can go beyond political posturing and lip service and have the kind of public conversation our city must have to promote the mental health of our children and families,” McCray added.