A pensioner was found dead in her house after waiting almost four hours for an ambulance to arrive.
The 81-year-old woman called 999 complaining of chest pains on Tuesday, according to a union.
Paramedics arrived hours later and forced entry to her property in Clacton, Essex, but she had already died, the GMB said.
The incident happened as political pressure grows on the government to reassure the public that the NHS can cope during the busy winter period.
East of England Ambulance Service (EEAST) said crews arrived three hours and 45 minutes after the initial call.
Dave Powell, regional officer for GMB, said the incident is ‘another example of how we are not coping’ with the NHS winter crisis.
‘My concern is now that we are actually suffering deaths whilst people wait for ambulances,’ he added.
‘On arrival, the crew had sufficient concerns to force entry to the property as the control room could not contact the patient via telephone.
Most popular on Yahoo News UK
Ex-wife of ‘black cab rapist’ John Worboys ‘disgusted’ over prison release
£50,000 worth of donations to ‘homeless hero’ thief Chris Parker to be returned
This is how Donald Trump’s extraordinary comb-over actually works
Warning over Facebook Messenger video ‘which hijacks PCs to mine cryptocurrency’
Drunk shoplifter who sued police for being Tasered during his arrest loses ‘excessive force’ case
‘Unfortunately, the patient was found deceased in the property and there was nothing the crew could do for her.
‘I’m sure this case is much more widespread than the public is aware of.’
EEAST previously said it has had to rely on taxis to take patients to hospital after struggling to cope with a surge in demand over the holiday period.
A statement on January 2 said the service received more than 4,100 calls on December 31 and around 4,800 on January 1.
‘To put this into content, the Trust’s average daily volume of calls is about 3,000 calls a day,’ it added.
Matt Broad, deputy director of service delivery, said on Thursday: “The Trust, as well as the wider NHS, is still experiencing incredibly high demand and is under extreme pressure.”
The incident came with temperatures predicted to plummet this weekend, putting further strain on health services.
NHS England urged people to stock up on medicines, check on vulnerable or elderly neighbours and get the flu jab.
A spokesman said: ‘Freezing conditions are forecast in some areas and evidence shows that the risk of heart attacks, strokes and other serious breathing problems increases as temperatures plummet.’
Sandy Brown, deputy chief executive at EEAST, said: ‘We do expect to see an increase in calls and we have additional resources prepared.
‘However, everyone can play their part and we are calling on the public to do things like check in on vulnerable members of the community, make sure you have sufficient over-the-counter and prescribed medicines, and most importantly, if you feel you need the NHS service, choose wisely and if you need to go to hospital, if possible, make your own way there.’