The East of England Ambulance Service is the worst performing trust in the country, a Watford Observer investigation can reveal.

Overworked crews are struggling to get to critical patients within the target time.

Ambulances have failed to turn up to patients, including those having heart attacks and strokes, within eight minutes more than any other ambulance trusts in the country between April 11 and May 9.

But experienced paramedics are leaving the trust amid “dire” working conditions.

Unions have called on ambulance bosses to improve conditions to prevent the staff exodus.

The trust’s data shows 41 per cent of critical patients were forced to wait longer for an ambulance to arrive in the first week of May.

But in April, it was the worst performing trust in the country for reaching patients in life-threatening conditions.

And analysis of the last four weeks shows the East of England Ambulance Service was the worst in the country when comparing how many times they were able to meet the target response time.

Almost half of ambulances did not reach people in conditions classed as "serious but not life-threatening", such as people having fits or diabetic episodes, within the same eight-minute target time.

One hundred and twenty three patients were also forced to wait longer than 40 minutes despite the call handler categorising it as an emergency call. Analysis of the figures showed the trust last met the government target in July last year.

Emergency calls were at record highs between April 2015 and March 2015, with more than one million people dialling 999.

Fraer Stevenson, UNISON branch secretary said: “In the last two years, the trust has recruited 800 student paramedics but 350 have left.

“We are losing paramedics who have 15/20 years of experience and they could have helped mentor and train the new staff.

“The trust needs to plan ahead. Hundreds of staff have decided to vote with their feet and if the management do not do something we will continue to lose more. It is a difficult place to be.

“I think staff pressures are a huge part of the problem. Demand has gone up, as it does every year, but this year it has gone up by a larger amount than it usually would. So if you couple staff pressures with the extra demand, it is a perfect storm.

“It is pretty dire.

“It is a very demanding role. But if you add the additional pressures, that is why hundreds of people are leaving. Our concern is that hundreds more will leave and we will be in a worse position next year.”

Robert Morton, chief executive of the trust, admitted it cannot cope with demand.

He said: “The sheer scale of growth in demand is masking some of the progress we are actually making.

“Right now, we do not have the capacity to deliver the services we are expected to deliver and we cannot continue to rely on short-term investment and hiring private ambulance services forever.

“That is why we are working with our commissioners on a long-term plan for sustainable and ongoing investment to service the ongoing increases in demand but we need to be realistic about timelines, as paramedics are not trained in weeks or months.”

Finance papers showed the trust spent £796,000 on private ambulance services in April alone. This was to boost performance.

There are 247 staff vacancies within the trust.

In 2014, the trust started recruiting 800 student paramedics. They spent a year training on the road with experienced paramedics. But many of them are now due to spend several weeks back at universities and this will take them off the streets.

The trust has insisted it will be hiring 150 associate ambulance practitioners this year, 100 graduate paramedics and 200 student paramedics. It says it will also train 100 ambulance care assistants to become intermediate practitioners.