Four care homes in Pembrokeshire say they may have to close before Christmas because of a row over their fees.
The homes' owners are going to the High Court to challenge what they are paid.
Eighty six people stay at Pen-coed, in Saundersfoot, Langton Hall, in Fishguard, Woodfield Care Home, in Narberth and Woodland Lodge, in Tenby.
Pembrokeshire council leader John Davies said the authority paid a similar level or more in fees than many others in Wales.
Care Forum Wales, which represents independent care providers, said the High Court hearing in Cardiff next week would decide whether the council should immediately start paying more money while the longer term dispute was resolved.
It said all four homes received excellent ratings from the care homes regulator, Care and Social Services Inspectorate Wales (CSSIW).
Barry Latham, senior policy advisor for Care Forum Wales, said the Welsh Assembly Government had issued guidance to local authorities that the fee levels they pay should recognise the provider's legitimate costs of delivering the service.
But he said not all local authorities in Wales were following the guidance.
He has been asked to give written evidence to the court by the owners.
"These cases appear to be symptomatic of wider problem in the social care sector which is causing a postcode lottery in relation to the provision of care in Wales," he said.
"As around 75% of residents in care homes are publicly funded, the fees which local authorities pay for their supported residents have a critical impact on the financial viability of care homes."
He said if the homes were closed he doubted whether alternative accommodation could be found in Pembrokeshire for all 86 residents, as many required specialist care for conditions such as dementia.
"We have been concerned for a number of years that local authorities are not complying with this guidance and setting fee levels too low," he added.
"We are gravely concerned that the current crisis in public sector funding is likely to encourage local authorities to place a greater downward pressure on the fees which they pay which could put more care homes at risk."
The Southern Care Group, which runs nine homes in Conwy, Denbighshire, Flintshire and Wrexham, went into administration two weeks ago.
Actively exploring options
Mr Davies said: "Care Forum Wales, has a view on fee levels but this is not one which is widely adopted.
"The responsibility of councils is to set fees. It is not a negotiating process.
"We are firmly of the view that we have done this fairly and we have used a nationally recognised financial model to assist us.
"We are confident that the council's position will be upheld by the court when the full facts are explained in the hearing in Cardiff on Tuesday."
He warned that if the council agreed to pay £500 per week to all homes in Pembrokeshire it would increase the authority's costs for residential and nursing home care by £2.25m.
"I can assure you that we are actively exploring options should these homes close and I recognise and fully appreciate the worry and concern this is causing."