“Patients can’t get into A&E because there isn’t an empty cubicle, let alone the staff, so they end up trapped in ambulances. Meanwhile A&E is full of patients who can’t be moved onto wards, because they are full of elderly people who can’t be discharged because there isn’t help at home,” he said.

In twelve months, the numbers waiting at least four hours before “handover” to A&E staff tripled, with 96 such cases in 2012/13, the figures show.

The longest delays were at Royal Cornwall Hospital in Truro.

On one day in March, one patient waited more than eight hours before handover, while two others waited more than seven hours.

Letters seen by this newspaper disclose that a month later, Ken Weyman, the chief executive of South Western Ambulance Service, warned the hospital’s chief executive that the equivalent of 14 crews were being lost each day because they were stuck at casualty units.

The situation had left the 999 service, which covers Cornwall, Devon, Dorset, Gloucestershire, Somerset, Wiltshire and Avon, with no ambulances to send to life-threatening calls, he said.

Earlier correspondence from Norma Lane, executive director of delivery at the ambulance service cites incidents in which six ambulances at a time were stuck parked outside the hospital.

The letter, seen by The Sunday Telegraph, says: “This is unacceptable from the views of patients waiting, as well as presenting serious risks to those patients.”

It continues: “The impact on our resources significantly compromises our ability to respond to life-threatening calls and extends serious risk to the public.”

At Stepping Hill Hospital in Stockport, a patient waited almost six hours last December, while at Tameside Greater Hospital, in Lancashire, there was a wait of more than five hours, according to disclosures under the Freedom of Information Act.

The vast majority of the longest delays were in the South, with 67 patients who called South Central Ambulance Service waiting four hours outside A&E, compared with 24 such cases the previous year.

In total, 18 patients waited more than four hours for handover Queen Alexandra Hospital, Portsmouth, with 13 such waits outside Royal Hampshire County Hospital and 12 outside Wexham Park Hospital in Slough.

In documents seen by this newspaper, Will Hancock, the head of South Central Ambulance trust, said queues at A&E meant one ambulance crew had been left caring for 10 hospital patients at once – putting them in danger.

His log discloses a knock-on effect on others calling 999, describing delays of 30 minutes for paramedics to see a patient with chest pains – which can signal a heart attack – and of more than 20 minutes in response to a person choking, and a young woman coughing up blood.

A second letter sent to Ursula Ward, chief executive of Portsmouth Hospitals NHS trust, last November, said the problems had caused delays sending ambulances to four further incidents categorised as “life-threatening”.

Patients also waited at least four hours at Broomfield Hospital in Chelmsford; Norfolk and Norwich Hospital; Southend Hospital;, Milton Keynes Hospital; Southampton General Hospital: Royal Berkshire Hospital in Reading; John Radcliffe Hospital in Oxford; Basingstoke and North Hampshire Hospital; Stoke Mandeville Hospital; Warrington General Hospital; Southport District General Hospital; Solihull Hospital, Royal Shrewsbury Hospital; Sandwell General Hospital; City Hospital in Birmingham and University Hospital of Coventry and Warwickshire.

South Central Ambulance Service said the delays were a “major concern” and work was underway to redesign A&E systems to tackle the problem.

Jo Gibbs, Chief Operating Officer, at Royal Cornwall Hospitals trust said: “Patient safety is always our number one priority and we work closely with the ambulance trust and our health and social care partners to manage the flow of patients into and out of our hospitals.

We have put measures in place to reduce delays in ambulance handovers and although emergency activity has remained high and the patients we are seeing are older, more seriously ill and have complex needs, there has not been a repeat of the exceptional circumstances that were seen in March.”

Portsmouth Hospitals trust said the waiting times were related to a number of factors including public demand and availability of community care.

Simon Holmes, medical director, said that for some periods the trust had adopted a policy of keeping a single ambulance crew as a handover team so other crews could get back on the road more rapidly.

NHS England said that Professor Sir Bruce Keogh, national medical director, is leading an urgent and emergency care review to address problems currently faced in urgent care, including ambulance services, which began public consultation earlier this month

Last year this newspaper revealed that Monitor, the regulator of NHS foundation trusts, had warned hospitals not to keep patients in ambulances in order to comply with the government target of treating all patients admitted to A&E within four hours.

Monitor said that hospitals who used the technique – known as “stacking” – risked “serious implications” for their patients and tied down ambulances needed to respond to emergencies.

Although the practice began under Labour, the extent of this has risen sharply under the Coalition. Local newspapers have found instances of as many as 14 ambulances queuing up outside a hospital A&E department.

In a letter to trusts last year, Monitor specifically warned hospitals against “gaming to meet health care targets”. “We would encourage all trusts to ensure that such practices are not taking place at your hospitals,” the regulator’s letter read. “Evidence of foundation trusts carrying out these practices would be taken very seriously by Monitor.”

The watchdog has the power to sack health trust boards or issue fines.

Ever since the Coalition was formed three years ago, ministers have pledged to protect the NHS from the spending cuts being felt across Whitehall departments and local government.

However, in his spending review last week George Osborne, the Chancellor, announced that councils would gain access billions of the health service’s budget used to pay for care for the elderly. Experts claims this will lead to a major squeeze on the NHS’s front-line services.

Under the new plans the NHS will pay £2 billion a year to local authorities to support those who need social care – up from an annual contribution of £1 billion. The government has said this will ease pressure on A&E departments by moving elderly people away from hospitals.