A heavily pregnant woman who lost her baby after she was repeatedly kicked in the stomach in a "sickening" assault in the street was forced to wait more than an hour for an ambulance that never arrived.
The London Ambulance Service has apologised after admitting police were forced to take the 21-year-old to hospital themselves when after an hour and ten minutes of waiting the ambulance had still not attended.
The victim, named in reports as Malorie Bantala, later lost her baby in hospital and remained in a critical condition following the attack near her home in Peckham on Monday night.
A spokeswoman for the London Ambulance Service said: "We were called at 8.16pm on 15 June to Talfourd Place, SE15.
"We are very sorry that we were unable to send an ambulance before we were cancelled by the police at 9.25pm and are now looking into the circumstances of what happened."
She confirmed that the LAS did not attend and that police officers took the woman to a South London hospital.
The spokeswoman said the first 999 call from a member of the public was assessed to be a "lower priority call" - or a category C call.
Miss Bantala, who was 32 weeks pregnant, was pushed to the ground by two men in motorcycle helmets who continually kicked and stamped on her stomach.
Scotland Yard said there was a "strong likelihood" that the two male attackers were targeting the unborn child and the attack was being treated as "akin to murder".
A 20-year-old man from south London, who was arrested on suspicion of child destruction and grievous bodily harm, is being questioned by police.
Detective Chief Inspector Robert Pack, from the Homicide and Major Crime Command, said: "This was a truly abhorrent and vile attack on a heavily pregnant woman who has now, tragically, lost her baby.
"The men who attacked her must have known the impact their actions would have when they kicked her repeatedly in the stomach.
"It is sickening to think someone would deliberately target a pregnant woman in this way."
He added: "Certainly we're treating it akin to murder."
Scotland Yard said the "brutal assault" happened as the woman walked home along Talfourd Place in Peckham at around 8pm.
The suspects - who are described as black and in their 20s - then ran off, still wearing their helmets, in the direction of Denmark Road.
A number of people heard screams and witnessed the attack outside a converted pub and rushed to the woman's aid after the men fled, before a member of the public alerted police.
Officers administered first aid at the scene before she was taken to hospital.
Mr Pack said the woman remained in a critical condition in intensive care but she had managed to provide an account of the attack to officers.
"From what we know at the moment, the working hypothesis is that it was targeted at that unborn child," he said.
"There doesn't appear to be any blows or physical force directed to her head or face. It seems to be all the violence was targeted towards the child."
He added: "There's absolutely no suggestion this is part of a pattern or spate of similar attacks. This is a one-off."
Asked whether the victim knew her attackers, Mr Pack replied: "Quite possibly."
Mr Pack told reporters that murder detectives were dealing with the case because of the "devastating impact" on the woman's life and the "sheer level of mercilessness involved".
A motorcycle has not been recovered by police and it was possible the attackers were wearing helmets as a disguise, he said.
Mr Pack added: "I have absolutely no doubt that someone out there has either heard something, or overheard something, or had someone confide in them.
"It's that sort of person that really needs to search their conscience and think 'This is not on, this is beyond the pale'."
Anyone with information is asked to contact the incident room on 020 8345 3985 or Crimestoppers anonymously on 0800 555 111.
Metropolitan Police Commissioner Sir Bernard Hogan Howe described the attack as "horrific".
He told BBC London 94.9 radio: "The fact that a young woman has been attacked and happened to be pregnant and the fact that obviously a child's life has been lost, you can't get much worse than that."
He added: "I hope people are reassured that these are very rare incidents, horrific when they happen. We take them seriously."