An elderly woman who called 999 complaining of chest pains died while waiting almost four hours for her ambulance to arrive, while in a separate case another pensioner died following a seven-hour wait for a hospital bed.
On Tuesday, an 81-year-old Essex woman called 999 complaining of chest pains, but when paramedics arrived at her Clacton home and forced entry into the property they found the woman dead, according to the GMB union.
East of England Ambulance Service (EEAST) said crews arrived three hours and 45 minutes after the initial call was made on Tuesday.
Figures released this week revealed that delays in ambulances getting patients to A&E departments in England have peaked at their highest level so far this winter, with 16,900 people waiting more than 30 minutes to be seen by staff at emergency departments over the Christmas week.
The Department of Health states that ambulance crews should be able to hand patients over to A&E staff within 15 minutes of arrival at hospital.
Failures to do so increases the risk to patients due to delays in diagnosis and treatment, as well as the chance their condition could deteriorate.
The figure was up from 11,900 the previous week, and included 4,700 patients delayed for more than an hour.
The number of people waiting more than an hour to be handed over to A&E staff during Christmas week nearly doubled on the week before, hitting 2,413.
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.
"I'm sure this case is much more widespread than the public is aware of."
He continued that the paramedics who discovered the dead woman were "devastated" following the incident.
"They're devastated because they're not in the job to find people dead, they're in the job to help people and keep them alive," Mr Powell said.
"It puts enormous strain and stress on people who are working really hard as it is.
"Three hours and 45 minutes is totally unacceptable for an elderly woman on her own with chest pains.
"Something has got to be done and the Government has got to wake up to this crisis."
EEAST has previously said that it has had to rely on taxis to take patients to hospital after struggling to cope with a surge in demand during the Christmas period.
On New Year's Eve and New Year's Day the service received more than a third more calls than normal.
Some 4,100 calls were made to EEAST on December 31 and around 4,800 on January 1, compared to a daily average of 3,000.
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."
In a separate case, a Portsmouth hospital has vowed to investigate after an 88-year-old woman died following a seven-hour wait for a bed.
Josephine Smalley spent five hours in an ambulance and another two hours on a trolley in a corridor at Queen Alexandra Hospital.
She died on New Year's Day, after having a heart attack and previously a stroke.
The pensioner's family called an ambulance after Ms Smalley suffered breathing difficulties at her home in Southsea on December 30.
Granddaughter Jessie Hirst, 27, said the family are "devastated" and told the Portsmouth News: "She should have been at the top of the list."
Theresa Murphy, chief nurse for Portsmouth Hospitals NHS Trust, said a full investigation into the death will be carried out.
She said: "The emergency department was under significant pressure over the bank holiday weekend and regrettably this meant that some patients experienced delays.
"Mrs Smalley was seen by our clinical staff and assessed within four minutes of arriving at the emergency department.
"Her condition was monitored but unfortunately she had to wait for some time before being treated.
"We're extremely sorry for the additional distress this will have caused."
The hospital has been under increased pressure, with 24 ambulances reportedly queuing outside during New Year's Eve.
The deaths come as hospitals in England cancelled 55,000 non-urgent operations in a bid to free up hospital beds and staff amid increasing winter pressures.
How big is the scale of the winter pressure?
Leading medics have warned every emergency department in the country is struggling to cope with winter pressures.
Some hospitals have declared themselves at the most severe pressure level while ambulance services have also expressed severe concern, with some even resorting to taxis to ferry patients to hospital.
Will winter pressures ease anytime soon?
The deaths of the two elderly women and the latest figures on hospitals in England come as temperatures are predicted to plummet this weekend, putting further strain on health services.
NHS England has urged people to stock up on medicines, check on vulnerable or elderly neighbours and get the flu jab.
A spokesperson 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."