Hertfordshire residents may have to wait "between three and five years" for the region’s ambulance service to turn around its poor response times.

A clinical capacity review by the East of England Ambulance Service revealed it needs an extra 421 employees, and 50 new ambulances, in the next four years.

More than 300 of those new members of staff will have to be recruited by 2015, and it is estimated that the additional resources required will cost in the region of £25-30 million per year.

The new resources are needed to help cope with an increase in demand of 3.2 percent, and a predicted increase of 60 incidents a day brought about by the new 111 non-emergency telephone number.

A paramedic, who asked to not be named, said: “To be honest everyone is so fed up now and morale is at rock bottom.

“Our cars are regularly waiting over an hour, sometimes two hours for back up. I can't see how the service is going to cope as we approach winter pressures.

“We are regularly being told that no back up is available. Our solo responders are under a lot of unnecessary pressure dealing with patients that are "time critical" but have no way of getting them to the hospital. Staff support along with morale is at an all time low.”

The trust has held a recruitment drive, but only seven paramedics have been hired in 2013.

The number of rapid response vehicles has increased but they have largely been sent to Norfolk and Suffolk, and the number of hours they are operational has reduced by 812 hours.

The report revealed the time taken for ambulances to arrive and then take a patient to hospital is "too long", with 42 percent taking more than 19 minutes, 25 percent more than 30 minutes, and six per cent taking longer than an hour.

The review pointed strongly to there being more rapid response vehicles and not enough ambulances.

It read: "There is still a substantial shortfall between the resources available and the resources required consistently to achieve current national and potential future local performance targets."

Dr Geoffrey Harris OBE, trust chairman, said: "Transforming our ambulance service is going to take time - possibly three to five years, but we have made a good start.

"We know the issues we have to address, we have a plan in place and we are making changes and seeing some early signs of improvement."

Andrew Morgan, chief executive, said: "It has taken us a long time to get to this point, but we are starting to make headway. The issues we faced were deeper and broader than anyone realised, but we are starting to make progress.

"Part of that is tackling sickness, which is going in the right direction, as well as the downward trends in our longer response times.

"Making this a high-performing ambulance service is going to require us all to pull together - staff, managers, stakeholders and the public."