The police have launched an investigation after the staff at one of the UK's biggest NHS mental health hospitals were caught mistreating their patients on camera.

They were filmed mocking, slapping, and pinching patients at the Edenfield Centre near Manchester.

The incident came to light during an undercover investigation by BBC Panorama. The series, titled "Undercover Hospital: Patients at Risk," was broadcast Wednesday night. The staff members could be heard using demeaning language while talking about the patients.

A female support worker was filmed mocking a patient for having to supervise her while going to the toilet. The hidden camera captured a woman being pinned to the floor. The young woman had been locked in a seclusion room for 17 days. Footage shows staff describing her as a "cancer" who "needs a good thrashing."

The 23-year-old woman could be seen sobbing, asking the nurses to "let her get up," but to no avail. "I can't believe you've done this again. You didn't even give me a chance," she could be heard saying in the video.

More than a dozen staff members have now been suspended by the National Health Service. An independent clinical review has also been commissioned.

"We are working closely with local and national partners including NHS England, the Care Quality Commission and Greater Manchester police to ensure the safety of these services. We will cooperate fully with all investigations," said the NHS.

"We owe it to our patients, their families and carers, the public and our staff that these allegations are fully investigated to ensure we provide the best care, every day, for all the communities we serve," it added.

Greater Manchester Police (GMP) said that they were reviewing the footage to identify offenders. The allegations involve 40 patients and 25 staff, per a report in the Manchester Evening News.

"In consultation with the Crown Prosecution Service, we are reviewing footage from Panorama with a view to prosecuting anyone who's captured committing a crime. Anyone who has concerns about care they or a loved one has received should contact us or Crimestoppers," said a GMP spokesperson.

autumn budget 2017
NHS logo Ben Stansall/AFP