An elderly woman lies partially clothed on a bed.

Standing over her, a male carer pushes her this way and that as he gives her a bed bath. "Ouch," she cries. He slaps her. There's no provocation.

The woman is 78 years old. She suffers from Alzheimer's. Her name is Maria Worroll. She's a resident of Ash Court care home in Kentish Town, London. Would we ever have known about her mistreatment if her daughter hadn't placed a camera secretly in her room?

The scene was broadcast last night by the BBC, the second exposé of abuse of elderly residents in care homes in less than a year. The previous scandal involved Winterbourne View in Bristol. Residents there were secretly filmed being dragged along floors and being slapped. How much more abuse is going undetected in rooms or homes without hidden cameras?

Ash Court had an "excellent" rating from the Care Quality Commission which has the responsibility of inspecting homes in England. Thanks to Mrs Worroll's daughter, Jonathan Aquino, the care-worker who delivered the slap, is serving 18 months for assault. Imagine how frightened and bewildered her mother must have been.

Also consider how corrosive incidents like these are. They undermine confidence in the elderly care system. They make old people fearful of how they will be treated when they become incapable of looking after themselves. They alarm the families of those who are already in care homes. How can they be sure their elderly mother or father hasn't been abused too?

Don't imagine that this is a problem confined to England just because the BBC has exposed two homes south of the Border. In May 2011 the Elsie Inglis private nursing home in Edinburgh was closed following the deaths of two residents.

An independent Parliamentary inquiry followed the Elsie Inglis closure. As a consequence, planned cuts to the Care Inspectorate in Scotland were partly reversed. An annual unannounced inspection regime was also introduced.

Age Scotland has welcomed the improvements but points out that 7.6% of Scotland's care homes are ranked as delivering weak or unsatisfactory care. There are 913 care homes in Scotland. That means more than 60 are weak or unsatisfactory. I don't know about you but they don't sound to me like the kind of place I would want to leave an elderly parent.

A spokesman for Age Scotland said yesterday: "Clearly there is more to be done." Indeed there is.

Quite rightly, the charity wants urgent changes to staff selection and training, including the employment in care homes of specialist dementia nurses. Age Scotland expresses alarm that the Scottish Parliament's Health and Sports Committee highlighted the practice in some care homes of medicating residents to "manage their behaviour".

Staff are the crux of the matter, and you can't talk staff without talking money. There's an army of care workers in Scotland – about 140,000. Some are in nursing or residential homes, others visit the elderly in their own homes or work with children. The wellbeing and happiness of the most vulnerable people in society – and one day that will be ourselves – lie in their hands. Their work is crucial. So how do we reward them? Too often they receive the minimum wage along with the dismal realisation of a working status that could barely be lower.

Daily they don their uniform, pull on a pair of rubber gloves and perform for others the routine and sometimes difficult tasks the elderly and the vulnerable are unable to manage themselves. While it isn't pleasant to wash a stranger or assist them in the bathroom, it can be managed with dignity or it can diminish both the client and the carer.

Transferring an infirm person from a wheelchair to a bed can be an efficient routine or a regular torment. It isn't just about physical technique. Tone of voice matters as does gentleness of touch. Maria Worroll was heaved under the arms and slung onto the bed like a sack of potatoes. She suffers from arthritis. Imagine the pain.

We beat our breasts, tear out our hair and call in the law when carers turn abusive. When they are exemplary, and so many of them are, we take them for granted.

This is not an apologia. I'm not about to suggest that carers are an army of angels. Many do the job only because they cannot find anything else. Some have a qualification; many do not. Of course they should all be trained, though I have to say I have known many carers and never spotted a correlation between qualifications and quality of care. Treating people with the courtesy and kindness they would like to be treated with themselves is what makes the difference between one carer and another.

What is crucial to decent care is time. Whoever dreamed up the 15-minute slot should be condemned to be in receipt of it throughout his or her own old age. That's not enough time to feed and water a beast. It takes half an hour to deal with a human being.

The Care Inspectorate points out that it cannot police character, that there are bad people and always will be. Professionalising care work will weed them out.

Putting care workers into nurse-led teams is an excellent idea, as Age Scotland suggests. I would go further and suggest every nursing home and residential facility has the equivalent of a parent teacher association. Residents would feel reassured if they felt the people with their best interests at heart had a voice.

At the moment families often find it hard to speak out. If there is a problem they fear giving offence to people whose goodwill they rely upon. If there is a major problem they often fear their complaint will be dismissed and their mother or father will suffer the consequences.

The Care Inspectorate offers an anonymous phone line to families. Complaints are followed up with an unannounced visit. Following the Else Inglis closure, it's on the case. But will enough improvement be possible while the carers into whose hands we place our most frail and dependent loved ones remain underpaid and unsung?

We need to get this system fixed. One day we too will be old and grey and full of sleep and bewilderment like Maria Worroll.