The London Ambulance Service will only spend 45 minutes handing patients over to A&E in a push to get ambulances back on the road for 999 calls.
A leaked email shows plans to tackle delayed handovers, where patients are stuck in ambulances outside hospitals for hours or face long waits for A&E staff to complete a handover.
Ambulance trusts across the country are struggling to respond to 999 calls on time, with delays handing patients to A&E playing a major role.
The NHS Standard Contract for 2021/22 sets a target that "all handovers between ambulance and A&E must take place within 15 minutes with none waiting more than 30 minutes".
However, immense pressure across the NHS means people can wait far longer owing to a mismatch between a hospital's capacity and the number of patients arriving at A&E.
The leaked email is understood to be from NHS England's urgent and emergency care lead for London, and sent to hospital managers.
Seen by ITV, it says: "From January 3rd we are asking that any patients waiting for 45 minutes for handover… are handed over immediately to ED (emergency department) staff allowing the ambulance clinicians to leave and respond to the next patient waiting in the community.
"If the patient is clinically stable the ambulance clinicians will ensure the patient is on a hospital trolley or wheelchair/chair and approach the nurse in charge of the emergency department to notify them that the patient is being left in the care of the hospital and handover the patient."
The email said that if the patient is not clinically stable, ambulance crews will stay with the patient until handover is achieved but added that the clinical responsibility for the patient lies with the hospital.
The email said the current "operational challenges" in the NHS are "very significant" and "this is a difficult time for everyone".
NHS palliative care doctor, Rachel Clarke, said on Twitter the plan was unsafe.
She wrote: "This isn't safe. This isn't a solution. There aren't the ED beds, the ED doctors, the ED nurses, the ED spaces. Or is the proposal here merely to pile up more patients in ED corridors?"
A spokesman for the NHS in London said: "The NHS is experiencing record demand for urgent and emergency care.
"We are working across London to speed up ambulance handovers at hospitals – where it is clinically safe to do so – so ambulance crews can get to more people who are unwell in the community.
"This is one of many ways we are strengthening the NHS response this winter, along with more beds, extra 111 and 999 call handlers, more ambulance clinicians and expanding the use of 24/7 control centres across the capital for urgent and emergency care."
'Shocking Reality of the Current NHS Crisis'
Liberal Democrat health spokeswoman Daisy Cooper said: "This move shows the shocking reality of the NHS crisis and is yet further proof that a major incident must now be declared across London.
"The Health Secretary must act now to save the capital's hospitals from being overwhelmed.
"Corridors and waiting rooms are already full with patients coping with severe pain. The Government cannot wait any longer to act.
"London's NHS is collapsing before our eyes. Ministers have spent months arrogantly dismissing or ignoring all warnings from senior health leaders and MPs.
"This is now a life-and-death situation for Londoners. The Government needs to recall Parliament immediately, declare a major incident and above all else, pass a plan to get the country out of this health crisis before more people die."
NHS figures show that 37% of handovers in the week to Christmas Day were delayed by at least 30 minutes, down from 41% the previous week but much higher than the 13% recorded at that point in 2021 and 11% in 2020.
This article contains information from PA Media.