The barely recognisable wreckage of the vehicles involved, a BMW 325 and a Volkswagen Scirocco, was strewn across a wide area near a bend on the A52 near Werrington, Staffordshire, which has long been regarded as an accident blackspot.
Ambulance crews who took the dead and injured to North Staffordshire Royal Infirmary were said to have suffered 'shock and pain' when they arrived at the scene of the crash at 10.40pm on Monday. The Scirocco had been ripped apart in the accident and lay in a field next to the road. It is understood the vehicle was too old to have been factory-fitted with rear seatbelts.
A spokesman for the Royal Society for the Prevention of Accidents said: 'We want to see retrospective fitting of belts in all cars that have anchor points. Seatbelts do save lives and certainly would have done in this tragic case.'
The driver, 31, who suffered pelvic injuries, lost two of her children - a six-year-old boy and his four- year-old sister - in the accident.
Two other passengers, a five-year- old boy and an eight-year-old girl who were not related, also died. All were from the Longton area of Stoke-on-Trent and had been returning from a 'special treat' at a restaurant and leisure complex near the scene of the crash.
The 38-year-old driver of the BMW and his wife, 36, suffered neck and ankle injuries respectively. Their 18-month-old son suffered head injuries. All three are in a stable condition. The family live in Staffordshire Moorlands.
Jim Perry, a local resident who was first on the scene, said: 'I was watching television when I heard a loud bang and rushed outside.
'The BMW was on the road pointing towards a field. The Scirocco was actually in the field. There were children lying in the road. It wasn't very pleasant at all. You dare not touch them because you don't know what that might do.' The crash happened on a bend near the Red Cow pub on the A52. Last year, a man died in a head-on crash near the scene of the latest tragedy.
Mr Perry, a driving instructor, said: 'Drivers come round the bend at atrocious speeds, and nothing has been done about it in the past. What does it take to get somebody to do something? Surely they could put some warning sign here.'
Geoffrey Hobbs, county surveyor of Staffordshire County Council, said the authority had reviewed the safety of the road after a number of accidents there and would look at the situation again.
Acting Chief Inspector John Baylay, of the Northern Traffic Division, said: 'This is the worst accident I have seen in my 29 years in the police force. My heart goes out to those involved.'
Police said that the families of those involved in the accident were 'extremely distraught' and had asked the authorities not to release names of the victims until an inquest is held.