A&E departments in Wales have recorded their worst ever waiting times with just 72.1% of patients seen within four hours in December.
This figure is down significantly from the year before which saw 77.8% of patients seen within the target time.
The next worse-performing hospitals are Ysbyty Glan Clwyd at 52.5% and Royal Gwent at 53%.
The target set by the Welsh Government is for 95% of patients to be seen in that time.
Last month there was a record high demand on the ambulance service and the highest number of attendance at emergency department for any December on record.
The Health Minister Vaughan Gething announced an extra £10m to help ease pressures on A&E.
The Welsh Ambulance Service saw their average daily red calls increase to the highest on record, a 23% rise.
The British Medical Association blamed the performance on a lack of resources and said there was an urgent need for more staff.
Analysis by Health Reporter James Crichton-Smith
Behind today's A&E figures showing record low performance against the targets, is an army of staff.
They work tirelessly, at all hours, to make sure those who need medical care are treated as quickly and effectively as possible.
But it's clearly very tough.
Here are the thoughts of one senior A&E doctor on what it's like on the frontline this winter.
I started by asking them about the four hour treatment target - and how some hospitals are managing to see only just over 50% in that time, as opposed to the 95% they should be.
"That's a good day...in relative terms!" they said. "There is that feeling of [them being] bad. It's not unusual. [It's] normal now. We are numb by it. [We] just get on with the work and try to do the best and safest we can."
On the subject of staff moral, they added it's "very low but credit to the staff they work hard to make it as comfortable and possible for patients."
I asked about the impact on safety. They said it "still continues to be unsafe for patients, relatives and staff. We have many serious critical incidences as well as near misses."