Embattled Correction Commissioner Joseph Ponte is stepping down amid an ongoing scandal over his improper use of a taxpayer-funded city vehicle, sources said.

Ponte, despite steadfast support from Mayor Bill de Blasio, will announce his resignation Friday — while de Blasio is out of town in Connecticut, sources said.

A growing chorus of critics, including City Council Speaker Melissa Mark-Viverito, had called for him to be ousted for taking unsanctioned trips to his Maine home in his taxpayer-funded municipal vehicle.

Ponte’s misuse of the SUV came to light in two bombshell Department of Investigation probes, showing how he and other top Department of Correction officials used city cars for numerous personal trips and how jails officials spied on DOI investigators probing them.

De Blasio had defended him, saying: “I think people are missing the forest through the trees. Joe Ponte has made a mistake. He’s acknowledged it; he’s paying back for the mileage. I am convinced he did not do anything wrong.”

But a DOI report found Ponte logged 18,500 miles of out-of-state travel over 90 days, mostly for trips to his home state.

Thirty-five of those days fell during the workweek, said the report, which was sparked by an anonymous tip that DOC staffers had been misusing their city-­issued cars. Ponte claimed he had put in a full eight hours on the job on 29 of those days.

All told, the commissioner — who ran Maine’s correction department until he was hired by de Blasio in 2014 to turn around the city’s violence-plagued jails — rang up $1,043.44 in fuel charges outside New York, and another $745.56 in E-ZPass tolls.

Ponte has since said he would pay back the money.

His resignation announcement will come two days after Mark-Viverito asked him to step aside.

“I do believe Ponte should step down,” she told reporters Wednesday. “I think he should consider it seriously at this point.”

Mark-Viverito said she made her feelings known over the weekend during a phone conversation with the mayor.

She would not divulge what de Blasio said to her.

Before word came late Thursday of Ponte’s plans to resign, he suggested he’d stay on as long as he had de Blasio’s support.

“I serve at the pleasure [of the mayor]. So we will see if [de Blasio] gets re-elected,” Ponte added at the time.

“He may not want to keep me.”