Local hospitals in London are being told to prepare for a reduction in their income of 15-25 per cent.
NHS London and the capital's primary care trusts, through offshoot organisation Healthcare For London, have produced a model for district general hospitals as more specialist care is centralised and many other services move into the community.
Its predictions are based on financial modelling and consultation with clinicians.
Without potential movement of services to elective centres and polyclinics the income loss is 15 per cent. With those included it is 25 per cent.
The report, A Local Hospital Model for London, says the drop will vary depending on commissioning decisions.
The speed of the reduction will depend on how quickly the reorganisation takes place. The Healthcare for London process is planned to last for 10 years.
Local hospitals could mitigate the loss by diversifying into, for example, greater rehabilitation and intermediate care; or provision of an on-site polyclinic, the report says.
It was written by former West Hertfordshire Hospitals trust chief executive David Law and Whittington Hospital trust medical director Celia Ingham-Clark.