Ambulance waiting at hospitals exceeds six years, BBC Wales finds
Ambulances have spent almost 55,000 hours waiting outside Welsh hospitals in six months, according to figures obtained by BBC Wales.
The ambulance service said there has been a "high increase" in delays in admitting patients due to NHS pressure.
This means in total ambulance crews have spent 2,269 days - equivalent to over six years - waiting to transfer patients to hospital departments.
The Welsh government said delays were unacceptable.
But it insisted most patients who needed to be treated quickly waited no longer than 30 minutes.
Opposition parties have called on minister to act to resolve the "potentially dangerous" situation, with one wait lasting more than five hours.
They said patients could be put at risk because emergency cover could be compromised elsewhere while ambulances are tied up waiting for patients to be admitted.
The figures obtained by BBC Wales via a Freedom of Information request also show that on 24,346 occasions in the six months to the end of February ambulances had to wait more than 30 minutes before patients could be admitted to hospitals.
Under Welsh Ambulance Service handover targets, emergency vehicles are supposed to spend no longer than 15 minutes transferring patients,
The longest single wait at a hospital during the period was five hours and 39 minutes.
The Welsh Ambulance Service Trust's latest performance report shows it only achieved 56.9% of patient handovers within 15 minutes, against the national target of 95%.
The ambulance service has previously calculated it faced a cost of £76 for each "lost" hour an ambulance spends outside hospital. On that basis the recent delays could have cost the service more than £4m.
It said while the needs of the sickest patients were given priority, it was working hard to make sure that all patients get the care they needed while waiting to be admitted.
A spokesperson for the ambulance service said it was working hard with all health boards where there were handover delays.
Dr David Samuel, chair of the British Medical Association's junior doctors' committee in Wales, told BBC Wales staff morale was at "rock bottom".
"I was speaking to a nurse earlier, one who has worked for almost 30 years, and she's never seen anything like it," he said.
"As she said, it's difficult to know that patients are probably going to be dying in ambulances and we can't help them and it's not our fault."
There have been many reports of ambulances queuing up outside Welsh hospitals in recent weeks.
Last month the Welsh government urged people to think before dialling 999, as A&E departments across the country faced "unprecedented" demand.
Earlier this month, a group of A&E consultants wrote to Health Minister Mark Drakeford warning A&E departments were "at the point of meltdown" due to overcrowding and a beds shortage.
Mr Drakeford said dealing with pressures in A&E will be a priority in the coming year.
Meanwhile, a wide-ranging review into the ambulance service's performance and structure, commissioned by the Welsh government, is due to submitted soon.
A Welsh government spokesperson said: "Lengthy patient handover delays are unacceptable and we expect all health boards to work with the ambulance service to keep delays to a minimum and continue to provide effective care throughout any delay, while the patient awaits handover.
"It is important to note that this is an international and UK-wide problem and the majority of patients in Wales who have a clinical need to be handed over to the care of A&E staff quickly are handed over within 30 minutes.
"Unfortunately there are occasions when there is a delay in handing over the patient to hospital staff."
But Conservative health spokesman Darren Millar AM said the figures highlighted "just how severe and potentially dangerous the problem really is".
Welsh Liberal Democrats leader Kirsty Williams AM added: "The problem of 'lost ambulance hours' has long been a thorn in this Welsh Labour government's side."
Plaid Cymru's health spokeswoman Elin Jones AM said the figures illustrated the "crisis" in A&E services in Wales.