Doctors are warning that accident and emergency departments are on the “edge of a precipice”, with patients forced to wait in ambulances for up to 11 hours outside hospitals.

Paramedics across Britain have reported queues of up to 20 ambulances waiting outside hospitals to transfer patients into emergency departments operating at full capacity. Every ambulance service in the country is now at the highest level of alert, the Association of Ambulance Chief Executives (AACE) said this weekend.

Martin Flaherty, the organisation’s managing director, said: “[The association] remains extremely concerned about the unprecedented levels of hospital handover delays which are occurring across the UK.”

A patient died last Monday after suffering a suspected heart attack in the back of an ambulance which had been queueing for more than two hours outside James Paget University Hospital at Gorleston-on-Sea in Norfolk. A hospital spokesperson said the patient was moved into A&E but “sadly died in the department”.

Worcestershire Royal hospital, Royal Shrewsbury hospital, Norfolk and Norwich university hospital and Darlington memorial hospital have experienced some of the longest handover delays. National guidelines say patients should be transferred from an ambulance to an emergency department within 15 minutes.

West Midlands ambulance service (WMAS) said its longest handover delay in August and September at the Worcestershire Royal was 11 hours and 46 minutes. It said three crews waited more than 11 hours in August to transfer their patients who stayed in the back of the vehicles.

Mark Wibberley, a senior emergency medical technician with East of England ambulance service and Unison Norfolk County lead, said: “The waits can be as long as six hours to hand over patients. It’s not acceptable.” Darlington Memorial Hospital reportedly had queues of up to 15 ambulances this month with crews waiting hours to transfer patients.

Dr Ian Higginson, vice-president of the Royal College of Emergency Medicine, said: “The last thing you want when you’re sick, frightened or in distress is to be waiting in an ambulance outside an emergency department. There has been a failure in the NHS to deal with this chronic problem. I am very worried these delays will get worse without effective planning on how to deal with it. It feels like we are on the edge of a precipice in terms of the quality of care we can provide for our patients.”

NHS figures published last week revealed that 2.1 million people attended A&E last month, the highest figure ever recorded in September. There were 946,707 answered calls for an ambulance to 999 last month, compared with 713,975 in September 2020, an increase of more than 30%.

Figures released to the Observer from the AACE reveal the hours lost to ambulance services due to hospital handover delays of more than an hour had increased from 4,700 hours in April 2021 to more than 35,000 hours last month. Handover delays can worsen ambulance response times, which in England are now the longest since the data was first collected in April 2018.

Prof Kailash Chand, a former deputy chair of the British Medical Association, died in July after suffering a cardiac arrest at home in Manchester. It took more than 30 minutes for North West ambulance service to arrive, compared with an average target response time of seven minutes. Chand’s son, Dr Aseem Malhotra, a cardiologist and chair of the charity the Public Health Collaboration, said his father would almost certainly have survived if the ambulance had not been delayed. He later found the service was on the highest level of alert because of the high demand.

He said: “These delays are absolutely shocking and there has been a complete failure to inform the public that ambulance services are on the highest level of alert because they are struggling to cope with the number of 999 calls. The system is broken.”

The chef and TV presenter Mary Berry, 86, has told how she had to wait three and a half hours for an ambulance after breaking her hip in August. She said she had been “perfectly happy” to wait and was treated at the Royal Berkshire Hospital in Reading.

Richard Webber, a paramedic and spokesperson for the College of Paramedics, said many hospitals were at capacity, with delays in discharging patients, and “it backs up and doesn’t allow the ambulances to offload”.

Hospitals say their staff are working under extreme pressure with record demands, but are working with NHS partners to reduce handover delay. Matthew Hopkins, chief executive of Worcestershire acute hospitals NHS trust, said: “We are extremely grateful to our WMAS colleagues and local healthcare partners who are working harder than ever to reduce waiting times and ease the problems caused by ambulances being delayed outside our hospitals.” North West ambulance service spokesperson said, “We offer our sincere condolences to Dr Malhotra and his family and can confirm that we have received a formal complaint from him. We are investigating the incident and will liaise with the family to discuss the matter further.”

An NHS spokesperson said: “Ambulances responded to a record 76,000 life-threatening call-outs in Septemberan increase of more than 20,000 on the previous high for this month, while 999 took nearly one million calls last month. Please help us to reduce delays by only calling 999 for life-threatening emergencies and contacting NHS 111 online or by phone for other medical assistance and advice.”