Patients are regularly waiting more than 50 minutes in ambulances outside south east Wales A&E departments.
The ambulance trust said it was addressing the issue with A&E
Over the last three months an average 106 vehicles a week have waited more than 50 minutes to deliver patients, the Welsh Ambulance Service confirmed.
Wales's biggest hospital blamed bed blocking and people needlessly turning up at casualty.
In February there were delays at two hospitals due to a high volume of 999 calls and a shortage of beds.
The University Hospital of Wales in Cardiff, said 160 of its beds were unavailable due to bed blocking.
In a statement, it said a third of emergency patients could be treated by a GP or pharmacist.
Hugh Ross, chief executive of Cardiff and Vale NHS Trust, which runs the hospital, said: "Our emergency unit has been under greater pressure this summer than in previous years.
"This has meant more patients have experienced delays, and the trust regrets that this has been the case.
"We know that more than 30% of people who come to our emergency unit could be treated by their GP or pharmacist, based on Welsh Assembly Government surveys."
He said 160 beds were unavailable because of delayed transfers of care - or bed blocking - and the length of these delays was "greater than in the past".
The ambulance trust said it was addressing the issue with accident and emergency departments as a matter of urgency.
The summer months are traditionally a quiet time but the ambulance service said it has been encountering problems at major district hospitals.
However, a spokesman said that figures had improved this week to an average of 85 ambulances waiting at hospitals for more than 50 minutes.
Mike Cassidy, director of ambulance services in Wales, said how often and how long ambulances were having to wait varied.
But, he added: "We've experienced some difficulties, maybe one or two days every couple of weeks just when the system overheats a bit and when demand is extremely high for us."
He said that since February most serious patients had been admitted immediately while some less serious cases waited three to four hours "on occasions".
Measures had been put in place to help ease pressure on A&E, such as employing GPs in ambulance service control centres.
Mr Cassidy added that it was important to make the public aware of the alternatives to calling an ambulance so resources were kept for the most seriously ill.
"I think quite often people call ambulances because they don't really know what the alternatives are, and I think it's about us trying to get information to the public to let them know what alternatives are available, for example, general practice and NHS Direct Wales," he said.
A spokesman for the ambulance trust said it was working with hospitals to find ways of easing the pressure on accident and emergency departments.
The ambulance service experienced a crisis in 2006 which saw several bosses quit.
It had failed to meet response time targets and was branded "appalling" and "unacceptable" in a report by a committee of AMs in March this year.
But in May, it claimed its performance was the best in its history, after hitting response targets for the second month running.
Just last month, its chief Alan Murray said he had helped restore some pride and credibility after one year in the job.
Have you been affected by ambulance queues at accident and emergency? Were you, or a member of your family left waiting in an ambulance for hours because there was no room in the hospital?
Below is a selection of your comments.
In this event it is NOTHING to do with the reliability/unreliability of the Ambulance Service. This is about the only two sectots within the NHS that actually do any work as everyone else just fobs off jobs. The guys and gals on the ambulances and A&E are frontline troops that take abuse from all quarters when they produce positive results time after time in spite of the lack of back up from NHS bosses, WAG and Joe Public.
R Pardoe, Radnorshire
I'm an experienced A&E nurse and part of my job involves helping patients access the right health care provider at the right time. My employer empowers me to treat patients myself, refer them to a GP, an A&E doctor or another health care professional. It's not rocket science but not many Trusts allow experienced nurses to use their skills in this way to help patients access appropriate care.As an example, if you cut your hand on glass you SHOULD be in A&E because you need to know there is no glass in your wound and that there is no damage to the nerves or tendons. Your GP is not the best person to treat you. Accident and Emergency departments are the experts in treating INJURIES (no matter how slight) or EMERGENCIES, but it's not always easy for the public to decide.
A&E nurse, Monmouthshire
I was on holiday in Monmouthshire a few months ago. (funnily enough A&E nurse.)
My seriously disabled wife fell ill during the evening. Luckily she had been visited by a district nurse that day and we had been given the out of hours number of the local doctor. I phoned this number and was told by a recorded message that the out of hours doctor was not available. My circumstances meant that I had no option but to phone 999. I explained to the emergency services what had happened and that we probably just needed to see a doctor. They decided that as the doctor was not available an ambulance must be deployed and my wife was taken to A&E. I'll just repeat that: I said I just wanted the services of the out of hours GP. THEY said that as one wasn't available, an ambulance would be sent. So who is responsible for clogging up A&E with patients who should really be seeing a GP?
T James, Cardiff
The issues surrounding access to urgent and emergency care are not new. The Department of Health in England successfully addressed most of issues with the establishment of the'emergency services collaborative'about four years ago - much work to maintain performance and standards continues. In essence the problem is not about isolated emergency departments or the ambulance service it is a hospital and primary care wide concern. The Welsh Assembly could learn much from the work done in England - the problems relating to emergency access are the same.
Mike Paynter, Somerset
I experienced a delay at A&E Morriston Hospital in February this year when my daughter was rushed by ambulance following a horrific injury to her face. I waited with an embarrassed ambulance crew for almost 45 minutes before care was handed over to the Hospital. Other ambulance crews (4) were also waiting to hand over care. It is a disgrace and money is being wasted tying up paramedics who may be needed to attend other life or death incidents. I complained to the then Health Minister Brian Gibbons only to be told that it was an operational matter for the Hospital concerned and the Welsh Ambulance Trust. What they need in these hospitals is the staff to be able to take over the care of patients to release the Ambulance staff. That cannot be too hard to sort out can it?
DAVID JONES, NEATH
My girlfeirnd was taken to Morriston Hospital a month ago with severe abdominal pains and she was forced to wait 3 hours for an ambulance to transfer her to Singleton Hospital for a scan on our unborn child. To me this is simply not acceptable as it makes me wonder what our taxes get spent on!!!
This is just another example of how our Ambulance Service in Wales is still failing, even after the arrival of Mr Murray. Fast Response times mean absolutely nothing if the patient can't get into a place of treatment.
J.Evans, North Wales
In a statement, it said a third of emergency patients could be treated by a GP or pharmacist. Then why not turn them away. People will learn. As usual this country is bending over backwards to please everyone where we need to prioritise and act on common sense!
Daniel Kynes-Hughes, Birmingham, UK
We experienced the same thing in May this year with my father. Llandough hospital was so busy patients couldn't be offloaded from the ambulances as there was no-where to put them in A&E - The situation is intolerable and the hospital staff would be the first to agree. Something urgently needs to be done about this unacceptable matter.
Rob Wheaton, Cardiff
About people 'needlessly turning up at casualty'. A few months ago I cut my hand on some glass. Nothing dramatic but deep enough for me to have problems in stopping the bleeding. So I went to my local GP and hoped the nurse would look at it for me. They refused, because I'd cut myself on glass, and sent me off to the casualty in Carmarthen. There I waited for an hour and the staff quickly treated and dressed the wound. Now why couldn't a trained nurse in a surgery do that? Can anyone explain?
Richard Crookston, Pencader, Carmerthenshire, Wales
It must be very difficult for paramedics when there are so many people calling an ambulance uneccesarily but I thougt that when an ambulance responded to any call it was up to the paramedics to determine whether the person needed to be taken to hospital or not. If they do not need to go to hospital the ambulance therefore does not have to take them. If the people are waiting in ambulances to be seen is this not a complete waste of an ambulance which could be needed in an emergency
sarah williams, POWYS
The problem is not a simple one. It would not make any difference whether you doubled the number of staff in the A&E departments or had twice the number of ambulances available. As Hugh Ross continues to say the beds are blocked. Until the Assembly Government sort out the problems of getting social care packages financed this will continue to be the case. They know what the problem is but because the sums of money involved are huge they chose to let the situation continue and blame the trusts and the ambulance service.
Chris Gill, Cardiff Wales
Sort it out by having a combined minor injuries unit Gp nurse lead and an urgent care and treatment centre within the acidnet and emergency unit the cuts bumps and scrapes are triaged through the minor injuries unit the asthams suspected heart attacks and other cases through the urgent care and treatment centre with full blown accident and emergency cases taken straight away to the accident and emergency rooms Not rocket sciene is it in fact frnak Dobson former health minister suggested this about ten years ago Aint rocket science is it
Kevin Taylor, Omagh North Ireland
We have to say the north wales ambulance service has been brilliant with my husband who had a major accident in work 2 years ago the para medics were really good with him and when he came home theyd come and pick him up for his clinic appoimtments every 4 weeks so we cant fault the service here.He was taken to the maelor hospital in wrexham who also gave him the best of treatment.
Mrs D Griffiths, Wrexham North Wales