Most family carers say they would have little to no trust in their local authority to offer adequate support to their loved one if they could no longer provide it, a disability charity has warned.
Sense said it spoke to one parent and carer who said he hopes his daughter dies before him as he worries so much about what would happen to her if he was no longer able to care for her.
With 1.3 million carers in England and Wales aged over 60, the charity said its findings raise fears of a "looming care crisis" for disabled adults with complex needs who risk being placed in unsuitable crisis care placements if their families were no longer able to care for them.
It found 95% of those who care for someone in their family said they would have little or no trust in their local council, with more than two thirds (67%) saying they fear what would happen to their loved one if they were no longer able to provide support themselves.
Three in four (75%) family carers say they have no long-term plan for what would happen if they could no longer provide support, research by the charity found.
It said Freedom of Information data has shown that just one in three local authorities know how many disabled adults are being cared for by family and friends at home, with only a quarter of councils able to support disabled people and their carers to make contingency plans for future care options.
Sense is calling on the Government to give local authorities more funding so they can provide better support for disabled people and their families, and for councils to ensure long term care plans are in place for disabled adults.
The research - based on a YouGov survey of 990 carers - found just 6% reported finding the process of planning for the future straightforward, with many saying they worried that a lack of quality care and a shortage of specialist services will mean their loved one's needs will not be met in the future.
Half of families said that they worry that funding cuts will impact the availability of local services for their loved one.
The report also heard from dozens of disabled people and their carers, including Mark Ward, 50, from Peterborough, who cares for his 24-year-old daughter Kerrianne.
She has epilepsy and learning disabilities and needs full-time support in all areas of her life, including with personal care and daily activities.
Mr Ward said: "I have no idea what would happen if I was sick. I expect that she would be affected by depression and more seizures likely.
"There is no one that knows her medication, how she can be manipulated, or gets scared in new situations.
"It's very stressful. I find myself hoping that she passes away before me. No parent should feel like this."
Sense deputy chief executive Richard Kramer said: "After a lifetime of caring, no parent or disabled adult should be left neglected and living in fear about the future.
"We need to tackle the pressures facing families with better planning for future care needs and greater investment in social care to combat this looming care crisis."
Councillor Izzi Seccombe, chairwoman of the Local Government Association's Community Wellbeing Board, said: "Councils are working hard to ensure all people, including those with disabilities and their carers, receive high quality, reliable care and support, as well as information and advice, to help them lead independent and fulfilling lives.
"Thousands of disabled people and their carers are currently supported by councils through care and support services and information and advice, and this report rightly calls for Government to ensure social care is adequately and sustainably funded so this can continue.
The president of the Association of Directors of Adult Social Services (ADASS), Margaret Willcox, said: "We recognise that families who care for disabled adults are often concerned about who else would provide care if they were not available.
"ADASS would encourage social services to be proactive in helping people plan, however, we also acknowledge the very real capacity problems experienced by many local authorities. In order to help with this, social care has to be sufficiently funded in both the short and the long-term. "
A spokeswoman for the Department of Health and Social Care said: "Carers are invaluable in supporting their loved ones and their own needs must be a priority too - which is why we changed the law to introduce better rights for carers.
"We know the social care system is under pressure -- that's why we've given an extra £2 billion funding and will publish plans this summer to reform social care to ensure it is sustainable for the future."