New video shows a Rikers inmate pummeling a correction officer and even hurling a trash can at the him without anyone lifting a finger to help the guard.

The clip obtained by The Post begins with the two standing chest-to-chest in a common area of the Robert N. Davoren Center, when the unidentified inmate shoves the officer — then the fists start flying.

They flail around the room for 15 seconds before the inmate gets a hold of the officer and slams him to the floor, climbing on top of the jailer to rain down with his fists before apparently helping the guard to his feet and socking him some more.

At one point a seemingly un-involved inmate can be seen casually crossing the frame.

Soon the tussle moves into a hallway, where the inmate shoves the correction officer out of the frame. Two more jailbirds fly in to see what the commotion is about — just as the first inmate hurls a plastic trash can at the officer.

It’s unclear whether he hit his mark, because the officer is out of frame, but moments later the trash can comes sliding back into view, leaving a trail of sludge as the inmate scurries off, the video shows.

It was not immediately clear when the video was shot, and the Department of Correction would not provide details other than the incident occurred “weeks ago.”

Correction Officers’ Benevolent Association President Elias Husamudeen decried the violence and said the city needs to hire more guards.

“This video and others like it are another reminder of why the officer to inmate ratio in the NYC DOC needs to change,” he said, questioning the wisdom of Mayor de Blasio’s plan to replace Rikers with smaller borough jails.

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