It was a hi-tech new system that was supposed to improve the performance of York and North Yorkshire's ambulances.

However, a new control room computer program introduced last year has led to a dramatic drop in ambulance response times - leading to fears that the lives of patients are being put at risk.

In December, the number of ambulances meeting the Government's eight-minute target for life-threatening "Category A" emergencies dropped to 60.7 per cent.

The figure is a massive 15 per cent below the national target, and nine per cent behind the local target of 69 per cent.

Although the rest of Yorkshire's trusts also failed to meet their targets, none missed it by such a wide margin.

Bosses at Yorkshire Ambulance Service admitted they were facing a challenging period and said the fall in performance was due to staff familiarising themselves with the new system in the York control room.

But York GPs have questioned why such a vital system was introduced before staff were properly trained, and raised fears that a patient might die unnecessarily while waiting for an ambulance.

Dr David Fair, of Jorvik Medical Practice, in York, said: "It is a very worrying situation and it makes you wonder whether the new system was properly piloted before it went live.

"I would say it was irresponsible if this wasn't the case, because it's patients' lives that are being put at risk. Category A calls are for people with life- threatening conditions, where speed is of the essence.

"These are patients who have had heart attacks, or maybe serious injuries from road traffic accidents, and the evidence shows that the faster people who have had a heart attack have CPR and electric defibrillation, the higher the chances of survival.

"My worry is that patients might die as a result of having to wait for an ambulance crew to arrive."

Selby MP John Grogan, called on Yorkshire Ambulance Service to "get their act together".

He said: "When a number of ambulance trusts were merged into a county-wide authority in 2006, it was argued that this should make the system more efficient.

"Clearly, this hasn't yet happened with response times, and I will be watching closely to see if an improvement is made in the coming weeks and months so that Government targets are achieved.

"Yorkshire Ambulance Service needs to get their act together, and quickly."

Glen Gears, who represents the York branch of Unison, stressed the delays were not the fault of the ambulance paramedics.

He said: "As soon as we get the call, we carry out our jobs as normal. The problem is in the control room and what goes on before we're alerted."

In a report to the board members of Yorkshire Ambulance Service, the operations director, John Darley, admitted the switch to a Computer Aided Dispatch (CAD) system had "severely hit performance".

So what’s in Category A?

Examples of Category A calls, which are all immediately life-threatening:
- Difficulty in breathing
- Heavy blood loss
- Loss of consciousness
- Chest pain
- Suspected heart attack
- Serious road traffic accident
- Head injuries
- Severe allergic reactions
- Fitting/convulsions
- Choking

He said: "The main contributory factor in the t rust failing to meet the 75 per cent standard for the months of November and December were continued challenges in coming to terms with the change to the CAD in the York communications centre.

"The trust has and will continue to operate all possible strategic and tactical contingency measures to mitigate the performance fall and recover the 75 per cent year to date position as soon as possible."

Assistant director of operations, Vince Larvin, said they had introduced the new system in a bid to improve performance and enhance the quality of care in the region.

He said: "The previous system did not meet the requirements of a modern ambulance service and was no longer supported by the manufacturer. The new system gives us extra capability to improve how we handle and respond to the needs of our callers.

"As staff familiarise themselves with the new system, a slight dip in performance is expected. All the training has been given, but it takes time for staff to come up to speed with any new system.

"However, there is no reason for any of the public to be concerned and we are already seeing an upturn in performance.

"Eventually the new system will help us to make response times even faster."