Martin Kilgallon, 47, said his father David, 71, was forced to lie with half of his body sticking out of the door because they were told by paramedics not to move him.
The frail great grandad is believed to have broken his right leg during the fall as his bones have become brittle due to chemotherapy.
He was diagnosed with myeloma, a cancer of the blood, which has weakened him considerably according to Martin.
Martin’s mum Rose-Mary, 69, rang him on Wednesday May 26 at 5pm after his father fell while walking through the back door of their home in Batley.
When she became concerned that he was left in a distressing position, she asked Martin, who lives just 10 minutes away, to rush to the property.
The pair and sister Helen Vine, 45, attempted to keep David warm with blankets and pillows, and held an umbrella for nearly four hours to keep him dry.
When the paramedics finally arrived at around 8pm, David was taken to Leeds General Infirmary where he underwent a surgery on his leg.
Martin said the paramedics were ‘brilliant’ but was fuming that his vulnerable dad was left to wait for nearly four hours – a time he says is ‘completely unacceptable’.
Martin, a businessman from Mirfield, said: “It’s not acceptable. I don’t blame the paramedics, but it’s unacceptable. It’s not just about my dad. You see stories of elderly people not being treated in the right way.
“My dad has brittle bones and is very weak, and he was in a lot of pain. To me it’s important that people feel safe, it’s not okay for people to be laying on the ground for three hours. Especially not someone who has cancer, who is very frail.”
“No one should ever have to wait more than an hour while their loved ones are in need of help.”
Martin said he has lodged a formal complaint against Yorkshire Ambulance Service NHS Trust but has yet to hear back.
The dad-of-five said: "I need someone up the chain to acknowledge the problem and try and solve it. Someone needs to be held accountable."
This comes just weeks after an elderly man who broke his hip was forced to lie in the road for over two hours outside a primary school just a couple miles away from David’s home.
A spokesperson for Yorkshire Ambulance Service NHS Trust, said: “We are very sorry to hear that the patient’s family has concerns about our response to this incident and our Patient Relations Team would be able to look into the specific details around this and liaise directly with the family.
“During the last few weeks the urgent and emergency care system has come under increasing pressure.
"We can confirm that this emergency call was received during a particularly busy period on Wednesday and we were doing our best to reach all patients who needed our assistance as quickly as possible.
"All calls are categorised according to the nature of the patient’s illness or injury and those in a life-threatening condition are always prioritised. For many patients our process often involves a call back from a clinician to assess their condition and check on any changes or deterioration.
“We wish this patient well in their recovery and would like to reassure members of the public that our priority is to provide a safe, responsive and high quality service to the people of Yorkshire.”
The NHS currently has four categories of urgency for ambulances.
Category 1 - Life threatening illness or injury such as cardiac arrest or someone who has stopped breathing. The response time for these calls is supposed to be within seven minutes.
Category 2 - Emergencies such as burns, epilepsy or strokes. Crews are supposed to arrived within 18 minutes.
Category 3 - Urgent calls such as women at the end of labour, less serious burns and diabetes. A target of under two hours is set for this category.
Category 4 - Less urgent such as diarrhoea and vomiting have a target response time of three hours or under.
The latest NHS data on ambulance response times shows that YAS's median response times in April were:
Category 1 - 7 mins 32 seconds
Category 2 - 21 mins 13 seconds
Category 3 - 54 mins 59 seconds
Category 4 - 1 hour 32 mins 59 seconds