Eleven units are under threat from closure, under reorganisation plans by NHS London. There are currently 31 A&Es in the capital.
Six of these may go in the west of the city alone, according to plans by the North West London Commissioning Partnership (NWLCP), seen by BBC London.
A&E services at Chase Farm Hospital, in Enfield, north London, and Queens Mary's Hospital in Sidcup, south London, are listed for closure.
The closure of the A&E department at King George Hospital in Ilford, east London, is also being consulted on.
And concerns have been raised by MPs in south-west London about the future of A&E services at Kingston Hospital.
Whittington Hospital may have to merge its A&E with the Royal Free Hospital, according to NHS plans which are going out for consultation.
The departments are being reorganised by the NHS as part of a city-wide review of how health services are delivered.
As a part of this shake up, the NWLCP is considering plans to shut five of the eight A&Es in the north-west London sector.
The current eight A&Es in the area are: Ealing Hospital, Hillingdon, Northwick Park, Central Middlesex, Chelsea and Westminster, St Mary's, West Middlesex and Charing Cross.
The NWLCP said one of the weaknesses in the health services for the area was the "current overprovision of certain specialties such as A&E and maternity" which was causing "financial and quality issues".
The document, entitled NWL Sector Integrated Strategic Plan 2009 - 2014, said St Mary's in Paddington would remain as an A&E, as it has already been designated a major trauma centre by NHS London.
On the basis of an initial review we have a concern that three Major Acute Hospital (MAH) sites are clinically and financially unsustainable
The other two are yet to be decided. But the NHS said more should close.
In giving its feedback on NWLCP's plans, NHS London said: "On the basis of an initial review we have a concern that three Major Acute Hospital (MAH) sites are clinically and financially unsustainable."
It added: "Given our misgivings, you should review this issue further and have helpfully agreed to refer to a 'maximum of three' MAHs in order to prepare the ground for the next stage."
The health authority also advised NWLCP that it should make it clear that there is the possibility that some hospitals may close to be replaced by polyclinics.
Dr Kevin O'Kane, acute medicine consultant, said patients will have to travel further
Describing NWLCP's plans for polyclinics as "weak", it said: "Turning to your proposals for local hospitals and elective centres, there is no reference to the numbers you believe to be sustainable across the sector.
"I know that you have a programme in place for reviewing all hospital care settings and the plan should, at least, signal the likelihood that not all the current sites will make the transition to either MAH or local hospital."
Rory Shaw, from the NWLCP, said: "There are no formal plans as yet for A&Es.
"This plan is about centralisation of some services in fewer locations.
"We want to centralise trauma in centres where there are teams who are good at this, and do it everyday."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.