Controversial plans for the future of the NHS would need to deliver £22bn of cuts in order to balance spending, the British Medical Association (BMA) has said.
The union's head, Dr Mark Porter, said there is a danger the plans are being "used as a cover for delivering cuts, starving services of resource and patients of vital care".
Health managers in 44 areas of England have been ordered to draw up the strategies, setting out how they will reduce costs, change services and improve care in the wake of a record £2.45 billion deficit for the last financial year.
The sustainability and transformation plans (STPs), some of which have been published or leaked, could see some hospitals, A&E units or maternity units close, and other services merged.
The proposal for Cheshire and Mersey includes the downgrade of at least one A&E department, while in north-west London, there are plans to reduce the number of sites offering a full range of services. Birmingham and Solihull's STP proposes a single "lead provider" for maternity care.
The new analysis by the BMA is based on savings figures found in documents from 42 of the 44 areas.
An accompanying survey of 310 doctors in England found 64% had not been consulted on STPs. A third of doctors had never heard of STPs and a fifth did not support their introduction, the BMA poll found.
Earlier this month, analysis by the King's Fund think tank said the plans had been kept secret from the public and barely involved frontline staff or patients.
It said NHS England had told local health leaders not to reveal the plans until they were finalised and had been approved by their own officials.
The national body even told local managers to refuse applications from the media or the public wanting to see the proposals under the Freedom of Information Act.
NHS England and some health experts argue that STPs will improve patient care and are necessary to fulfil Health Secretary Jeremy Hunt's plan for full seven-day services.
But campaigners say they are just a way of cutting services.
Dr Porter, chairman of the BMA's council, said: "Improving patient care must be the number one priority for these plans. Given the scale of the savings required in each area, there is a real risk that these transformation plans will be used as a cover for delivering cuts, starving services of resource and patients of vital care.
"It is extremely concerning that the majority of doctors have not been consulted on the plans, particularly as ministers have been so keen to insist that all stakeholders would be involved.
"STPs have the potential to generate more collaboration and the longer-term planning of services based on local need. But it is crucial that any plans about the future of the NHS must be drawn up in an open and transparent way, and have the support and involvement of clinicians, patients and the public from the outset.
"At this stage nobody can be confident that this has happened."`
Shadow health secretary Jonathan Ashworth said: "The financial crisis engulfing our NHS is staggering. The Tories are starving it of the cash needed and it is patients who are suffering as a result.
"These warnings that the proposed changes to local services in STPs are overwhelmingly driven by cuts - £22 billion of them - will set alarm bells ringing and rightly so.
"It's amazing that the Government can claim that these plans are clinically driven when two thirds of doctors say they haven't even been consulted.
"What's been revealed so far are drastic proposals to cut beds and services. It's simply not acceptable for these decisions to made behind closed doors.
"The BMA must be listened to and all these plans should now be published so patients, carers, families and those who work in the NHS can have their say."
The BMA said the cuts would need to be achieved by 2020/21 to achieve financial balance.
NHS medical director Professor Sir Bruce Keogh said: "It cannot be right that on any one day in England over 5,000 people are stuck in a hospital bed when they don't need to be.
"Our NHS has constantly adapted to improve services for patients, taking advantage of new opportunities and making common-sense changes in areas that really matter to patients - making it easier to see a GP, providing more specialist services in people's homes, speeding up cancer diagnosis and offering help faster to people with mental illness.
"We are talking about steady incremental improvement, not a big bang, tackling things doctors and nurses have been telling us for years.
"By continuing to adapt to a changing world, the NHS will be able to secure a better service for future generations."