Ambulance service miss emergency response times
The Welsh Ambulance Service failed to meet its response time target for the most urgent cases for the seventh consecutive month.
Latest figures show in December they succeeded in responding to only 56.1% of the most urgent (Category A) calls within eight minutes compared to a target of 65%.
The figures show a 2.3% drop in performance compared to November.
The Welsh Ambulance Service said it had recently faced "significant pressure".
A spokesman said: "During the month of December 2012 we dealt with 38,135 emergency incidents across Wales, an increase of almost 12% on November's figure, 34,168.
"In recent months, the healthcare system across Wales has faced significant pressure with increased cases of winter-related illnesses, such as flu and sickness viruses, and the ambulance service in general continues to experience a higher volume of calls.
"We would like to reassure the public that the trust is firmly committed to delivering the improvement aims of its Working Together for Success modernisation programme and will continue to work with health boards and other partners to improve our services for the people of Wales."
"We also require the support of the public and would encourage them to only dial 999 and attend Emergency Departments for life threatening and serious illnesses and injuries - remember to keep emergency ambulances for your emergencies
Welsh government health minister Lesley Griffiths announced a review into the service last November.
Of the 38,135 emergency calls in December, almost 15,600 were Category A calls.
December's figures show the ambulance service responded to 12% more emergency calls than the previous month.
Before the latest figures were announced, Roy Norris, former chair of the Welsh Ambulance Services NHS Trust, said people would be wrong to think that the simple answer was to have more ambulances.
He said the Welsh government review of the service would probably look at why ambulances are sometimes forced to wait long periods outside busy hospitals with patients waiting to be admitted.
"There has got to be an entire system review of why it is ambulances are held, why hospitals can't clear people through the emergency department and it will probably be looking at why people can't be discharged from hospital when they are ready to be discharged," he told BBC Radio Wales.
Welsh Liberal Democrat leader Kirsty Williams said: "The figures released today have shown that ambulance response rates in December were the lowest of any month in 2012.
"While paramedics and technical staff are striving for excellence, they are facing immense pressure and having to work with increasingly stretched resources."
The ambulance service performed worst in Rhondda Cynon Taf responding to just 43.5% of the most urgent calls within eight minutes, figures reveal. It performed best in the Wrexham with a 72.0% response rate.
The all Wales target of responding to the most urgent calls is 65% but the target set is lower (60%) for response times in each unitary authority area.
The figures show the ambulance service only hit its 60% local performance target in six of the 22 unitary authority areas at Cardiff, Swansea, Pembrokeshire, Denbighshire, Conwy and Wrexham.
In six unitary authority areas the ambulance service responded to less than half of the most urgent calls within eight minutes at Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Neath Port Talbot, Torfaen and Bridgend.
The Welsh Conservatives say the results of another dip in response times comes as it has obtained figures that shows a reduction in the number of ambulances in Wales has dropped from 256 to 244, along with the closure of several stations.
"It is extremely worrying that performance has dipped considerably at a time when ambulance stations and vehicles have been reduced," said Conservative health spokesman Darren Millar, AM for Clwyd West.
The Conservatives say the figures have been revealed in a written response to questions put to health minister Lesley Griffiths.
The Welsh government has been asked to comment.