Some councils in England fear budget pressures will hit care services which help elderly and vulnerable adults live at home, a BBC survey has found.
Out of 87 English councils surveyed, 46 said they were concerned about funding for services.
They said many aimed at preventing or delaying people developing more dependent care needs could be affected.
Charities urged councils to continue to prioritise social care spending.
The Association of Directors of Adult Social Services warned there would be "tough decisions" to make.
A total of 58% of England's councils responded to the survey, conducted as part of BBC English Region's Living Longer project which looks at how areas of England will be affected by the ageing population.
Almost all councils - 86 out of 87 - said they were already investing in intervention services such as reablement, the intensive temporary care in the home to help people regain their independence.
But 46 said they feared budget pressures next year and beyond will impact upon these services.
Michelle Mitchell, charity director at Age UK, said thousands of frail and vulnerable people relied on home care services.
"Even seemingly modest cuts could see a quarter of a million older people lose the essential home-based care and support they rely on," she said.
"It's down to each local authority to protect the most vulnerable and frail in their community by promising to preserve local care funding and spend every penny of the £2bn earmarked by the Treasury on social care."
A spokesman for the charity Carers UK said: "It is absolutely vital that local councils continue to prioritise spending on social care.
"Unless they do, the dignity and independence of older and disabled people will be undermined and more families will be forced out of work and pushed to breaking point in order to care for them."
In the government Spending Review, Chancellor George Osborne promised an extra £2bn for social care by 2014/2015.
But there are fears that because of the overall budget cuts faced by local councils, the extra money, which is not ring-fenced, may not be put entirely into social care.
The support charity Carers UK and the Nuffield Trust think-tank have expressed concern that social care may not end up seeing all the extra funding.
The Association of Directors of Adult Social Services (ADASS), which represents heads of social services across England, said councils would be doing all they could to protect care services but warned it would be "tough".
Richard Jones, president of ADASS, said: "Since adult social care can comprise anything up to 50% of councils' controllable budgets, protecting social care services will be very challenging in face of a 28% reduction in LA (local authority) funding from government.
"We will have to make some very tough decisions given the overall level of resource that will be available."
He warned councils will have to consider increasing the amount they charged those who are eligible to make a contribution for their care.
"Inevitably people will have to pay more towards the care they receive; the level of fees councils pay for services will be reviewed and in some places eligibility criteria, which define who is able to get a service, might have to be changed," he said.
"Until the full impact is known in December of the final amount of resource that will be available to each council, it will be difficult to calculate just how tough some of the decisions will have to be."
'Quality of life'
Care services minister Paul Burstow said the extra £2bn would mean no council needed to reduce access to social care.
He said: "We are investing in reablement services that get people back on their feet after a stay in hospital.
"By using telecare and developing preventative services, councils can cut their costs, reduce pressure on the NHS and improve the quality of life of their residents."
The BBC research revealed 72 of the local authorities surveyed were considering changing, either increasing to decreasing, the amount they charged for care services next year.
Some councils suggested that changes in charging may be tied in with changes to personal care budgets.
These budgets, allocated by local authorities, allow social care users to choose how their services are provided.
In October, the Audit Commission warned that many councils were struggling to hit a target that would see 30% of eligible people offered their own budget by April 2011.
The BBC survey found more than half of councils questioned estimated that between 25% and 35% of service users will be receiving budgets by the end of March 2011.
In Scotland, free personal care for the elderly has been in place since 2002.
Under the policy, over-65s who live at home are not charged for personal care services, while those paying their own way in care homes get £156 a week for personal and £71 for nursing care.
The latest figures showed the policy provides for more than 50,000 elderly people and costs the Scottish government £376m a year.
In Northern Ireland, a recent survey suggested many elderly people were worried about reduced incomes, higher taxes and cuts in vital services.
The Centre for Ageing Research and Development report found pensioners in Northern Ireland were at a significant risk of poverty in comparison to their counterparts in Great Britain and the Irish Republic.
In Wales, the Assembly Government is preparing for a launch early next year of a White Paper into the future of social care. The current legislation operates on an England and Wales basis and although social care is a devolved matter, the UK benefits system that impacts on charging for care is not.
In considering the way forward for Wales, the Assembly Government is working closely with the UK Government. Ministers emphasise that any new system must promote independence, choice and control for everyone who uses care and support services as well as being affordable to government, individuals, and families in the long term.