A shocking undercover BBC Panorama programme filmed at a Prestwich Hospital mental health unit showing a "toxic culture" of abuse of patients airs tonight, Wednesday.

The broadcaster said its probe has found verbal abuse and bullying at The Edenfield Centre and has released some of the vile insults that were caught on camera.

The BBC said secret footage at the unit shows staff taunting patients in vulnerable situations, using inappropriate restraint - according to experts - and faking paperwork intended to ensure patient safety.

The BBC’s undercover reporter, Alan Haslam, spent three months as a healthcare support worker at The Edenfield Centre’s medium secure unit in Prestwich, following whistle-blower allegations of poor staff behaviour and patient safety at the hospital.

The secret footage he captured shows staff mocking, slapping and pinching patients, the BBC has said.

Greater Manchester Mental Health NHS Foundation Trust which runs Edenfield told Panorama it was taking the allegations “very seriously” and had taken “immediate actions to protect patient safety”.

A number of staff members have been suspended, and the trust said it was working with Greater Manchester Police, the independent healthcare regulator the Care Quality Commission and NHS England.

The Edenfield Centre cares for people held under the Mental Health Act who are at serious risk of harming themselves or others, including some patients from the criminal justice system.

Wearing a hidden camera, the BBC said the reporter saw:

• Staff swearing at patients, taunting and mocking them in vulnerable situations - such as when they were undressing - and joking about their self-harm

• Patients being inappropriately restrained - according to experts who reviewed the footage - as well as being slapped or pinched by staff on some occasions

• Some female staff acting in a sexualised way towards male patients

• 10 patients being held in small seclusion rooms - designed for short-term isolation to prevent immediate harm - for days, weeks or even months, with only brief breaks

• Paperwork intended to ensure patient safety was frequently falsified - showing staff had done patient observations when they hadn't.

Dr Cleo Van Velsen, a consultant psychiatrist, said the BBC's footage showed a "toxic culture" among staff of "corruption, perversion, aggression, hostility, lack of boundaries", which was undermining patient recovery.

Prof John Baker, an expert in mental health nursing at the University of Leeds, said: "It doesn’t feel safe.

“I think you are quite clearly seeing toxic staff and there has been an awful lot of hostility towards patients.... which is really concerning."

One patient Claire (not her real name) is diagnosed with schizophrenia and is not allowed to go to the bathroom alone for her own safety.

A female support worker was filmed humiliating Claire for having to supervise her while going to the toilet, complaining to her face about "having to look at you’re a******* where biohazard f****** waste comes out.”

In a sign that boundaries between patients and staff had broken down, on another occasion Claire sat on the lap of the same support worker, who said: “If you fart, I will actually kill you.”

The support worker then pulled aside the patient's clothing and repeatedly slapped her bare skin.

A senior nurse was among those who watched, laughed and jeered as Claire was slapped.

Most of the time nurses are in charge of the wards.

One nurse was filmed refusing to check on a crying patient, Olivia, who has self-harmed and tried to kill herself.

The BBC is only identifying patients who have given their consent, alongside their families.

Staff members laughed and joked that: “Olivia's only crying” and “if she slit her throat, you'd know it” because “she'd tell everybody about it.”

Staff were also filmed using demeaning language when talking to patients about their bodies.

This was often passed off as a joke, but patients said they felt bullied and dehumanised.

Olivia said staff had called her a “fat ****”, before claiming they had been joking.

The 22-year-old's mother said Olivia had in the past stopped eating and drinking because she believed she was overweight.

Olivia said: “It's not funny, it's not a joke.”

Another time, when Claire was due for a weekly injection, she hid her head under a blanket.

Support workers and the senior nurse with them did not try to persuade her to comply, but instead were filmed dragging her by the wrist from a chair and into a room down the corridor.

The support worker mocked Claire again as staff held her down on a bed and exposed her body for the needle, saying "as if we'd choose to see your arse" and calling her a "cheeky b****" as she protested.

After giving the injection, the staff locked Claire in the room, telling her they would keep her there for an hour as they laughed at her through the glass in the door, before letting her out a few moments later.

Dr Van Velsen said the members of staff acted "like a gang, not a group of health care professionals.”

She said: "It's against any policy I’ve ever seen about restraint in doing this.”

The code of practice for mental health workers says restraint and other "restrictive interventions" should only be used to take control of dangerous situations and stop anyone being hurt, not for punishment.

But the BBC filmed one patient being restrained after hospital managers said she had been shouting and verbally abusive.

Harley, an autistic woman who was at Edenfield due to self-harm was sitting on the floor when at least eight members of staff picked her up and dragged her away, screaming.

Harley was being restrained to take her back into seclusion, where she had already spent more than two weeks.

Patients held in seclusion are locked in a small bare room, usually without any possessions, with only occasional breaks in an adjoining room.

There is a window for natural light, but it doesn’t open.

There is no fresh air or access to the outside.

At one point a nurse is filmed saying staff wanted her kept in seclusion because staff "need a break from her.”

Dr Van Velsen said: "You cannot deprive somebody of their liberties because staff are fed up with her."

Patients are only supposed to be confined to one room and isolated from others for short periods when there is an "immediate necessity" because they are likely to harm other people.

It should not be used as a punishment or threat, or because of staff shortages, guidelines say.

Staff told the BBC's undercover reporter that Alice (not her real name), a patient who they said had attacked staff, had been in seclusion for more than a year.

Guidelines for mental health hospitals say they can keep patients segregated for long periods to protect others on the wards.

But the hospital must have the approval of a team of experts, consult the patient's family where possible and give the patient additional space, including access to an outside area.

Edenfield's seclusion rooms have a bed, shower and toilet, all of which can be observed by staff from an adjoining room.

However, some have mould, peeling paint, a smell of sewage and windows that don't open.

During one 30-minute break from seclusion, Alice spoke about her blanket and teddy bears, comforts which she had been allowed on a previous ward.

A support worker told her: “You’re lucky you’ve not got a straw f****** bed in there.”

She added: “If I was to run a place like this, they'd get straw bedding, eat it as much as you want, you're only gonna s*** it out and fertilise the garden.”

On another occasion, staff were filmed trying to give Alice her anti-psychotic medication twice, because there appeared to be a breakdown in communication.

Asked what would happen if she had too much of the drug, a nurse said: “She'd probably just die.”

While the majority of patients filmed being mistreated by staff were women who had been sectioned and had self-harmed, some patients held in Edenfield had committed violent crimes.

Experts said staff showed a worrying lack of boundaries even with these patients.

One man, serving a life sentence for murder, was filmed writhing on the floor and on a bed as a female support worker grappled with him and tickled him.

Afterwards, she said: "You get away with murder here, don’t we? Can you imagine if I got caught by bosses?”

Vulnerable female patients were also seen being mistreated by male staff.

A male support worker taunted a woman with a history of self-harm as she undressed, saying he would turn his back because “I don’t want to be mentally scarred again.”

The same support worker pinched her twice, the second time whilst bending her arm backwards.

"It's an assault," said Dr Van Velsen when she viewed the footage.

Among the staff's most important duties are patient observations.

These are checks to ensure patients are safe, made every 15 minutes, or more frequently for patients at higher risk.

Observations were frequently missed or carried out poorly.

Records of the observations are important because they affect decisions about care and can show that patients were being properly looked after, in the event that they hurt themselves or anyone else.

A nurse was filmed telling a support worker to falsify the records.

He said: “Here, sign some of these things, say you've done them.”

He also asked the undercover reporter to join in saying: "Want to pretend you were doing obs?"

Hospital employees complained of understaffing and burnout and sometimes support workers were left on their own, with no nurse on the ward.

There was a shortage of nurses for adult secure wards on 58 occasions.

This was during one five-week period this summer, according to records from the trust which runs Edenfield and seen by Panorama.

Professor Baker said there should never be a shift without a registered nurse on the ward but added that recruitment problems in mental health care were "no excuse for the abuse we’ve been seeing in the footage.”

The BBC has reported the findings of its undercover investigation to hospital management and the Care Quality Commission, which regulates secure units.

Greater Manchester Mental Health Foundation Trust said senior doctors at the trust have undertaken clinical reviews of the patients affected and it had also commissioned an independent clinical review of the services provided at the Edenfield Centre.

They said: “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.”

The Quality Care Commission said it was in contact with the trust and other agencies, including the police to ensure the safety of patients at Edenfield.

Panorama Undercover Hospital: Patients at Risk will air on BBC One at 9pm tonight, Wednesday.