More than 23,000 allegations of abuse have been made against carers working in people's homes across the UK.
The data comes from a Freedom of Information request submitted by the BBC Radio 4 programme File on 4.
The United Kingdom Homecare Association, which represents 2,000 care companies, described the findings as "horrifying" and blamed cuts to local government budgets.
The Department of Health said it had given councils up to £7.6bn of funding.
The BBC asked every council in England, Scotland and Wales with responsibility for social care for the numbers of allegations of abuse and neglect made against home carers contracted by local authorities.
In Northern Ireland, the BBC sent Freedom of Information requests to health and social care trusts.
This revealed that between 2013-14 and 2015-16 there had been at least 23,428 safeguarding alerts across the UK, but only half the councils provided data.
Most of the alerts related to care provided in England.
Last May, a hidden camera caught husband and wife carers Maurice and Deborah Campbell assaulting and abusing 86-year-old dementia patient Dora Melton in her Peterborough home.
Mrs Melton's daughter Elizabeth Budnik told the BBC about the moment she had watched footage of her mother being attacked.
She said: "He hit her round the head with real force.
"He didn't even stop to think.
"He just lifted his hand up and hit her across the head as hard as he could."
Last September, the Campbells both pleaded guilty in court to ill treatment and wilful neglect.
Maurice Campbell was sentenced to 28 months in jail.
His wife was sentenced to 38 weeks in jail, suspended for two years.
The Campbells were employed to care for Mrs Melton by Sagecare, through a contract with Peterborough City Council.
A Sagecare representative said it was "appalled and shocked" by the abuse but gratified justice had been done, adding it continued to provide care for Mrs Melton.
Peterborough City Council said there had been a thorough investigation into the incident.
But File on 4 discovered prosecutions were rare, with just 700 of the 23,428 alerts resulting in police involvement and only 15 prosecutions.
Gary Fitzgerald, from Action on Elder Abuse, said: "The overwhelming majority of abuse is criminal in nature and never gets prosecuted.
"It gets social worked, but it doesn't get prosecuted.
"If there's an investigation, rarely will the police be involved.
"If the police are involved, they don't actually want to upset that old person, so they won't prosecute.
"So you might get a police caution if you're lucky, or there might be no prosecution at all."
Rise in complaints
The vast majority of alerts were raised about elderly people, with more than 9,700 involving people aged over 80 like Dora Melton, and 164 about people who were aged over 100.
Councils were asked by File on 4 for the reasons behind the alleged abuse.
- more than 12,300 alerts concerning neglect
- 2,400 reports of psychological abuse
- more than 3,400 alleged incidents of physical abuse
- more than 400 claims of sexual abuse
It is not possible to find out whether all these reports were valid and fully investigated.
But the local government ombudsman, Michael King, said there was a growing problem over standards of home care.
Ombudsman complaints about homecare rose by 25% last year to 372, and 65% of them were upheld.
He told the BBC: "What we see is just the tip of the iceberg.
"We see a whole range of complaints: failure to look after people's personal care needs, helping them with eating, with their own hygiene, helping them with medication, all sorts of day-to-day tasks that people should be getting help with."
A Department of Health official said: "This government has introduced tougher inspections of care services, given councils access to up to £7.6bn of dedicated funding for social care and will continue to challenge local authorities that do not fulfil their duties under the Care Act."
File on 4: Neglect - The Story of UK Homecare is on BBC Radio 4, 28 February at 20:00 GMT - catch up on BBC iPlayer Radio.
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