Letterkenny University Hospital spent a whopping €1.17 million on private ambulances last year.
The figure is outside of the service offered by the National Ambulance Service which covers the Co Donegal medical centre.
Letterkenny spent the most of six hospitals covered by the Saolta Group which figures showed spent a total of €3.3 million on such private ambulances in 2015.
The figure represents a considerable 50% in private ambulance costs on 2014.
The figures were released to Fine Gael TD for Galway West-South Mayo, Hildegarde Naughton.
Ms Naughton said the increased spending was “utterly mind-boggling.”
She said “It would appear that the system underpinning the provision of public ambulance transport is dysfunctional.
“There are huge savings to be made if Intermediate Care ambulances would be made available outside core hours.”
The other hospitals in the Saolta region include University Hospital Galway, Portiuncula in Ballinsloe as well as Mayo, Roscommon and Sligo hospitals.