Patients have reportedly been "stuck in ambulances", waiting up to 25 hours outside a hospital in Bridgend.
A source who works within the health service said vehicles outside A&E at the Princess of Wales Hospital were "going nowhere" over the Easter bank holiday weekend, as there were no beds available inside the building to move patients to.
The source, who wished to remain anonymous, took a photo outside the hospital at 8:15pm on Monday 18 April, where numerous ambulances can be seen parked up.
The Welsh Ambulance Service said it is aware of a patient who waited in excess of 24 hours to be handed over to the care of Princess of Wales Hospital staff this weekend.
The service's Executive Director of Operations said unfortunately, extended waits at emergency departments "are not uncommon" and hospital handover delays are an issue affecting ambulance services across the UK.
The source told ITV Wales News that in recent times, there is often a problem with ambulance service crews being "stretched" and long waits outside hospitals due to a lack of space inside.
They said: “Often, there are no ambulances in my local area because they have been called into other health boards and then remain stuck outside another hospital all night with a patient.
"Ambulance crews remain positive despite having to work well passed the end of their 12 hour shifts, simply due to there being no room at hospital. Unwell patients are sometimes waiting up to 20 hours plus in the back of an ambulance, of which we are all powerless to do anything about.
"The amount of new housing estates have shot up over the last five years and yet the amount of ambulances has remained the same. However, I’m not sure if getting more ambulances on the road is the solution.
"There is no clear solution but it’s unbelievable to see the ambulance service constantly being stretched so far, so often."
They said that the Princess of Wales Hospital has a small, local A&E and is "relying" on Community First Responders, who are volunteers, to care for patients arriving in ambulances who have had cardiac arrests.
The source added that they were speaking out in the interest of patient safety.
Responding to these claims, Lee Brooks, Executive Director of Operations at the Welsh Ambulance Service, said: “Hospital handover delays are a long-standing and well-documented issue which is affecting ambulance services across the UK, including here in Wales.
“Sadly, extended waits in the community and at Emergency Departments are not uncommon, which is a result of a number of factors, all of which we are working on, both as an organisation and as a wider system.
“In the meantime, we’re asking the public to use us responsibly – the NHS 111 Wales website should be your first port of call for health advice and information, and you should also consider your nearest pharmacist and Minor Injuries Unit.
"Please only call 999 in a serious or life-threatening emergency so we can protect our precious resources for those who need us most.”
Cwm Taf Morgannwg University Health Board, who oversee the Princess of Wales Hospital, also appealed to the local community to use services like the NHS 111 website and pharmacies in non-emergency situations.
Dom Hurford, Medical Director at Cwm Taf Morgannwg UHB said: “Along with all other health boards in Wales, we continue to face extreme pressures on our emergency care departments. We are working closely with our colleagues in the Welsh Ambulance Service Trust and local authorities but, despite the very best efforts of our teams, we are seeing an exceptionally high level of demand on our services.
“Our communities can be reassured that our emergency, hospital and community teams are working incredibly hard, and that we will always prioritise patients with the most serious life-threatening injuries or illnesses.
“We appeal to everyone in our communities to understand the pressures we are facing and to always consider using our alternative services as a first port of call, including the NHS 111 website and local pharmacies. Non-emergency attendance at our Emergency Departments has a major impact on our ability to deal with the most seriously ill patients, and reduce waiting times for all.”