Pensioner Dorothy Manns waited over 10 hours to see a doctor but died just one hour after receiving help.
Prime Care, which provides Herefordshire's out-of-hours medical response, has apologised and said an official investigation is under way.
Jeffrey Manns who found his mother dead in bed, said: "It's diabolical, really. If I had called a vet to my sheep, he would have been here within 20 minutes."
Mrs Manns, of Much Marcle, who died of bronchial pneumonia with heart and lung complications, was struggling for breath on the day she died.
Her daughter-in-law, Rosemary Manns, said she made four phone calls to Prime Care.
Prime Care in turn made three phone calls to the family home at Stone Cottage, each time saying a doctor would come.
Rosemary said: "Would she still be here if a doctor had seen her sooner? None of us know.
Helped
"But she could have been helped earlier and would not have had to suffer as she did."
Mr Manns said: "I am not concerned about compensation, I don't want this to happen to anyone else and I want an explanation."
The family made their first call to Prime Care at 10.30am, with the doctor finally arriving at 9pm. They have yet to receive an explanation as to why it took so long.
Jeffrey's brother Tom, said: "It was on my mother's medical record that she should see a doctor within one hour of one being called."
Prime Care provides the out-of-hours cover for Herefordshire Primary Care Trust and the PCT's director of health development, Simon Hairsnape, said a report was being compiled by Dr Andrew Knight, the local medical director of Prime Care.
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