Watch ITV Wales' National Correspondent Rob Osborne's report
Performance against the eight minute ambulance response target is now the lowest on record.
The percentage of red calls receiving a response within eight minutes was 50% in October, down by 2.3% on the previous month.
It comes following months of pressure on 999 services, with reports of long waits for ambulances across the country.
Last month, military personal were drafted in in an effort to help ease pressure on ambulance crews.
The Welsh Ambulance Service has stressed that it is too early for the military’s intervention to have had an impact but did add that it should be reflected in November’s statistics.
Lee Brooks, director of operations at the Welsh Ambulance Service, said: "Subpar ambulance response times are a symptom of the pressures across the entire health and social care system.
"Issues being felt in other parts of NHS Wales, like delayed discharges which can hinder flow through hospitals and lengthen ambulance waits at the ‘front door’ of the Emergency Department, have a direct consequence for us because fewer ambulances are available to respond to patients waiting in the community.
"Coupled with staff absence exacerbated by Covid-19, and a significantly higher volume of calls, our ability to get to patients quickly has been significantly hampered in recent months, and we’re sorry to all of those patients who have had a poor experience.
“Fifty troops re-joined us in mid-October, and a further fifty joined us the following week, and it’s enabled us to send more ambulances to more patients, more quickly – for patients in our ‘Amber’ category, it’s taken up to an hour and a half off our response time."
Latest NHS statistics at a glance
The average time patients spent in emergency departments has also reached a new record high of three hours and seven minutes.
The latest month’s data shows that 65% of patients in all NHS emergency departments spent less than 4 hours in the department from when they arrived.
This is well short of the 95% target and was: 1.9 percentage points lower than the previous month, 12.3 percentage points lower than the same month in 2020.
People behind the statistics
Responding to the statistics, Darren Hughes, director of the Welsh NHS Confederation, said: "The NHS in Wales is currently facing unsustainable pressures, from all angles – problems facing social care, the ongoing impact of Covid-19, increasing demand for urgent and emergency care, as well as primary care, staff shortages and of course, the backlog of treatment.
"These statistics show the unrelenting high levels of demand the ambulance service and emergency departments are facing, with October seeing the highest number of immediately life-threatening (‘red’) calls made to the ambulance service since records began.
"We welcome the Welsh Government’s announcement of investment in diagnostic equipment, but without addressing staffing problems and wider system issues at play, there is only so much the NHS can do to address waiting times.
"It’s critical that funding and resources are focused on alleviating pressures facing the social care sector to assist in reducing the bottleneck, ensuring medically fit patients can safely be discharged into the community, freeing up much-needed capacity in the NHS.
"However, we need to be honest with the public that winter is going to be extremely difficult.
“The whole system is working together to find solutions to solve the problems, improve patient flow, manage high demand and keep people out of hospital where possible, but the pressure on the system is higher than at any other point during the pandemic.
“NHS leaders are very mindful that behind these statistics are people, both patients and the staff who are working day-in, day-out to do all they can to keep patients safe. We cannot thank them enough.”
Commenting on the latest figures, the Welsh Government said it doesn’t expect to see progress on waiting times until spring.
A spokesperson said: "The latest data shows pressure on our health and care system continues to grow.
“We have invested an extra £248m this year to transform the delivery of services and tackle waiting times, but because of the ongoing pressures and effects of the pandemic, we don’t expect to see real progress before the spring.
“Earlier this year we provided an additional £25m to go towards supporting the transformation of urgent and emergency care services to deliver the right care in the right place, first time.
“The ambulance service has also received funding for the recruitment of the equivalent of 120 staff.”