More than 1,800 Caerphilly County Borough residents waited over an hour for a first response after calling 999 for an ambulance last year.
Across Wales more than 28,000 ambulance callers did not receive a first response within an hour but 27, 684 were labelled Category C – neither serious or life threatening.
The statistics were released to the Welsh Conservatives under the Freedom of Information Act.
The Tories claim they show a failure in the NHS in Wales.
But the Welsh Government said the number of Category A calls not attended within an hour was 321 across Wales, less than 0.1% of all emergency calls.
Almost 21,000 calls were ‘Health Care Professional Admissions’ where admissions or hospital transfers are booked in advance with a time-scale suiting the seriousness of the incident.
A Welsh Government spokesperson said: “We expect all patients to receive an appropriate response in a timely manner, determined by their clinical need. We expect health boards to work closely with the ambulance service to ensure patients receive the care they require.
“The ambulance service receives more than 350,000 emergency calls a year and without looking into the individual cases it is not possible to understand why 321 of the Category A calls were responded to in more than an hour. This represents substantially less than 0.1% of all emergency calls.”
Welsh Conservative Shadow Health Minister, Darren Millar AM, said: “There are deeply ingrained problems within our emergency care services and these figures lay bare their true extent.
“Despite the hard work of frontline staff, more evidence of severe delays and unacceptable waits make for hugely distressing reading.
“No-one should be left hanging around for this long after dialling 999, especially in life-threatening situations.
“While committed staff put in long hours and huge sacrifices, the Welsh NHS continues to struggle to deliver a step change in performance as a result of Labour’s record breaking NHS budget cuts.
“Until these cuts are reversed, we will continue to see Labour Ministers starving hospitals of resources and pursuing a downgrading and centralising agenda which puts lives on the line.”
• In April Plaid Cymru highlighted concerns over staffing levels in the ambulance service in the Aneurin Bevan University Health Board area.
Freedom of Information statistics revealed that staff numbers fell below contracted levels on 280 days out of 365 last year.
Information obtained by party revealed that in one month – January 2014 – there was not a single day when the staffing numbers met the rostered levels.
South Wales East AM Lindsay Whittle said: “These are quite shocking figures.
“There were just 85 days during 2013 when staffing levels for ambulance staff in Aneurin Bevan were at the levels they should have been.
“This compares to 226 days in the neighbouring Cwm Taf Health Board.
“And what is particularly worrying is that in the first three months of 2014 on 74 days out of 90 the expected staffing levels were not met.
“There will obviously be times when shifts will not be covered for reasons such as sickness and annual leave but the position in Aneurin Bevan cannot be acceptable. This indicates a service that is being stretched far too thinly.”
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