A doctor in Germany regularly travels hundreds of miles from his home to fill in shifts for an out-of-hours service in north Wales.
The trust says there is a shortage of local doctors
Dr Johannes Wantzen, 49, is employed by Gwynedd Local Health Board and provides cover in Penrhyndeudraeth and Pwllheli.
But despite the long journey for the shifts, the doctor does not claim travelling or accommodation expenses.
The health board said that his services are only required when local doctors cannot be found to cover shifts.
It said that 95% of the shifts are covered by GPs from the area but doctors from other areas fill for the remaining 5%.
The board said a shortage of local doctors has meant that they have to use the services of the doctor from Germany and GPs from other areas.
Dr Wantzen provides out-of-hours cover at Bron y Garth Hospital near Penrhyndeudraeth and Bryn Beryl Hospital near Pwllheli when the trust is unable to find a local doctor to cover the shifts.
But despite the long journey to north Wales from Germany, Dr Wantzen pays for the travelling and accommodation costs out of his own pocket.
Peter Liptrot, Nurse Executive of the health board said the good working conditions offered appealed to many doctors on their books.
"There is no truth whatsoever in the claim that the German-based doctor is refunded his flight and other travelling costs to get to Bron y Garth Hospital," he said.
"The doctor does travel regularly from Germany to work in Gwynedd, but he is not being paid any expenses, which he meets out of his own pocket."
He said that the doctor is paid an hourly rate of £53 for a normal eight-hour shift and is provided with an ambulance car driver for home visits.
"This particular gentleman is on our books and he is normally available to work a few shifts of say four to five days at a time," he said.
"He then returns home to Germany and becomes available again whenever we need his services.
"The rate of pay is no secret and it is exactly the same as we pay local GPs for working such shifts, namely £53 per hour, or £80 on Bank Holidays."
But the trust insisted that the doctor was only asked to cover shifts when local doctors could not be found to cover them.
"It is no secret that we have a couple of GPs from away on our books who work regularly for us, but any travelling and accommodation costs are met by the doctors themselves," said Mr Liptrot.
"We don't pay the high rates GPs can claim elsewhere in the UK, but some prefer coming here because we provide good working conditions for them, which includes the ambulance car driver," he added.