A woman in agony with a broken leg was forced to wait for nearly an hour for paramedics to arrive.
The woman was lying in the mud in the Sir Francis Barker recreation ground in Chessington on Wednesday afternoon, with her crying granddaughter nearby.
A spokeswoman for London Ambulance said it had reached the call within 47 minutes.
She said that the woman had been classified as C4, the lowest category possible, as she was conscious and breathing.
Landscaper Tom Sweeney, whose boys Daniel, 19, and Ryan, 16, found the middle-aged woman and helped her, said: "I am shocked that she was categorised as C4. Even to be there for 47 minutes lying there with a child, I think it is unacceptable."
He said: "The boys were playing football in the park when they saw a toddler standing there crying her eyes out.
“They also noticed what looked like someone lying next to the toddler who was trying to reach up.
"They walked over and saw the old lady lying in the cold in the muddiest part of the park."
Mr Sweeney, who lives in Chessington, said the woman, whose name was Maddie, knew she had broken a leg, so his son Daniel called an ambulance.
Another woman nearby said she had tried ringing the lady’s daughter to ask her to collect the toddler.
He said: “My son Daniel covered up the lady with his coat and helped her to straighten her leg while putting his football training bag under her head and waited until the ambulance arrived.
“When the ambulance arrived she was in absolute agony. My two sons had to help to lift up the stretcher because the stretcher was too heavy for the female paramedics.
“I was amazed that it had taken so long for them to respond.
“My sons were getting worried for the lady and this worry was only taken away by the old lady’s reassurance things would be OK.
“I am very proud of the boys and what they did.”
A spokesman for London Ambulance said: "We can confirm we were called at 12.25pm on 19 February to reports of a woman who had fallen over in Barwell Business Park, Chessington.
“She was reported to be alert and breathing normally with an injury to her leg and so the incident was not categorised as a life-threatening emergency.
“An ambulance crew arrived on scene at 1.12pm. Staff treated the patient, reported to be in her 40s, for a leg injury and she was taken to Kingston Hospital.
“Although we did arrive within the time we are expected to get to patients in non life-threatening conditions, we would like to apologise if any distress was caused."
The service used to have a target for reaching serious but non-life threatening 999 callouts within 19 minutes but it was scrapped by the coalition in 2010.
The inquest of a missionary from Worcester Park last year heard Fiona Moore, medical director for London Ambulance, admit that they were suffering from a nationwide shortage of paramedics to deal with increased callouts.
The inquest heard that London Ambulance aims to attend the serious but not life-threatening category callouts within 20 minutes, although this standard was only achieved in around 65 per cent of cases.
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