Fife patients are being refused treatment by NHS Tayside, it has been claimed.
Campaigners say they have been told by senior staff that patients referred to the neighbouring health authority are routinely being turned away.
People in north-east Fife have had the option of being treated by NHS Tayside for many years.
However, Liberal Democrat councillor Tim Brett said the arrangement appeared to be breaking down.
He said “It has been made clear to me that NHS Tayside is refusing referrals from NHS Fife and most concerning is this is happening more often.
“The matter has been raised with me by senior staff at NHS Fife as well as GPs and patients.
“We are supposed to have a national health service and neighbouring health boards should be working closely together to benefit patients.”
North East Fife Lib Dem MSP Willie Rennie said locals had raised the issue with regards to the proposed closure of the GP out-of-hours service in St Andrews.
“I am worried to learn NHS Fife doctors are now telling us referrals are being repeatedly refused by NHS Tayside and the problem is increasing,” he said.
A spokeswoman for NHS Tayside said there had been no change in its response to clinical referrals and no change to its acceptance of appropriate referrals from Fife.
She said Tayside and Fife out-of-hours services had a long-standing agreement which means patients from Tayport, Newport and Newburgh can be seen in Dundee or Perth primary care emergency centres.
Since last April the service has agreed to temporarily extend this arrangement to Cupar, Leuchars and St Andrews overnight.