The National Ambulance Service has come under fire after a vehicle transporting a transplant patient broke down on its way to hospital.
Politicians have called for a full and independent investigation into the service, which is overseen by the Health Service Executive, following what they have described as an "appalling" and "inexcusable" incident.
Fianna Fail health spokesman Billy Kelleher said the breakdown was evidence the ambulance service is being stretched beyond its limits.
"This is not the first high-profile incident involving the ambulance service in the past number of months and it seems to me that since there was a reconfiguration of services, the ambulance service is being stretched and staff are being put under enormous pressure," Mr Kelleher said.
"It is imperative that Ireland's ambulance service is maintained properly and that all ambulances are fully roadworthy at all times. This involves investment and Health Minister James Reilly must ensure the service is adequately resourced. Patient safety is being put at risk and immediate action is needed before a life is lost."
It is understood the ambulance, which was carrying a patient from Cork to Dublin on Thursday, ground to a halt on the outskirts of the city.
It is believed the ambulance may have run out of fuel.
According to reports, the patient had been on a waiting list for a lung transplant when they got a call to travel to a hospital in the capital for the operation.
The patient had to be driven the rest of the journey in a garda car, which had been escorting the ambulance, following the breakdown.
"I find it appalling and wholly unacceptable that an ambulance transporting a seriously ill patient for a life-saving operation broke down because it ran out of fuel," Mr Kelleher said.
The National Ambulance Service confirmed it had launched its own investigation into the matter, but Sinn Fein health spokesman Caoimhghin O Caolain said the health minister also has questions to answer.
"Whatever the circumstances, whether running out of diesel or a mechanical breakdown, it is inexcusable," Mr O Caolain said.
"But for the Garda escort, this man, scheduled for a transplant operation, would have lost this important chance for life.
"The National Ambulance Service is clearly in need of urgent address. This was not an isolated incident. Is the service fully fit for purpose and dependable at all times?"
He added that he will be raising the issue at next week's Oireachtas Health and Children Committee.