£400m welfare benefit could be devolved to Wales
Responsibility for a major welfare benefit could be transferred to the Welsh government, it has been revealed.
The UK government is considering devolving Attendance Allowance, which is paid to over-65s with a physical or mental disability.
Officials said existing claimants would be unaffected, with a transfer of "equivalent spending power" to Wales.
The Welsh government said it was "extremely cautious" about how a change would be funded.
Attendance Allowance is currently paid at either £55.10 or £82.30 a week to about 100,000 people in Wales at a cost of about £400m.
It helps cover some of the costs associated with ensuring those who need personal care get help with things like washing and dressing.
The UK government will now begin a consultation on devolving the benefit to English councils and "to Wales".
If it is devolved to Cardiff Bay, Welsh ministers could manage the budget themselves or pass it on to Welsh councils.
But Age Cymru and Carers Wales have told BBC Wales they are concerned it could put the benefit at risk.
"We have serious concern about the future of Attendance Allowance under these plans," said Graeme Francis from Age Cymru.
"It's a vital part of the welfare state and helps delay the need for formal care services.
"Devolving it would mean it's no longer a ring-fenced benefit, and the Welsh government faces big financial challenges."
In addition, Age Cymru warned that Wales does not run a welfare system at present, so there would be new costs in administering the payments, leading to "less money for the actual benefit".
'Not called for'
The Welsh government said it wanted to see the "ramifications in full" of the proposal, including details on how Attendance Allowance would be funded in the future.
"We expect to see this in the UK government's proposed consultation, but let's be clear this is something we've never called for," a Welsh government official said.
"We share the concerns of Age Cymru and Carers Wales, and we are particularly mindful of what happened when the UK government devolved council tax benefit, when they top-sliced the budget."
A Plaid Cymru spokeswoman said while Labour had proposed scrapping Attendance Allowance when in government at Westminster, the party felt it was "right that Wales has greater responsibility for our own welfare".
"It is up to the Welsh public to decide who runs vital services, and we know that the Tories cannot be trusted to look after the most vulnerable in society," she said.
Responding, a spokeswoman for the UK government's Department for Work and Pensions said: "As was announced in the Local Government Finance Settlement, the government will consult on devolving more responsibility to local authorities in England and to Wales to support older people with care needs, including people who, under the current system, would be supported through Attendance Allowance."