The financial outlook of the National Health Service is "dire", a leading doctor has warned.
In his bleak New Year message to doctors, Dr Mark Porter, chairman of the council at the British Medical Association, said that the NHS is "struggling just to keep pace".
He said if the health service was a country it would "barely have a credit rating at all".
Dr Porter said efficiency savings are failing to keep pace with increased costs.
He said: "The period between Christmas and the January credit card bill can be one of nervous denial, but we eventually face up to our excesses and pay for them, in the gym or in the bank.
"The NHS is in a different situation. The financial outlook is dire, but if there ever was any extravagance in the 25 years I have worked in the health service, I must have been off that day.
"The NHS is struggling just to keep pace. A growing and ageing population, public health problems like obesity, and constant advances in treatment and technology are all contributing to push NHS costs well above general inflation."
Dr Porter added: "The numbers overall are so bad that if the NHS were a country, it would barely have a credit rating at all. The Nuffield Trust has estimated that if the NHS budget continues only to keep pace with general inflation, there will be a shortfall of between £44 billion and £54 billion in England by 2021-2022, unless there are productivity gains.
"But even with a 4% productivity gain every year, the funding gap would still grow to as much as £34 billion. It would take savage cuts to even begin to find this much money out of further 'efficiency' savings."
He said that NHS staff have "borne the brunt" of the Government's NHS efficiency drive - the health service has been charged with making £20 billion in efficiency savings by 2015.
"The National Audit Office said the NHS had made the 'easiest' savings first," he said.
"They were certainly not easy for the doctors and other healthcare staff who were made to bear the brunt. And it was not easy for the patients and staff every time a vacancy is not filled, a ward is closed, or a clinic is cancelled."
He said that "fundamental change" to the service is required but added: "Though not necessarily the kind of change most of us would want. A senior NHS leader warned recently at a policy gathering that efficiency savings would not be enough in the years ahead, and that the NHS would have to 'take out capacity'. That translates as cutting services to patients."
And since the Government's NHS reforms, which came into force in April this year, people working across the NHS in England are unsure of who is in charge.
"A major problem, in England at least, in that in a post-Health and Social Care Act world no-one really knows who is in charge," he said.
"Too often, service change decisions are driven by a mishmash of political and financial imperatives, alienating the local communities that the services are meant to serve."
Dr Porter also made a dig at comments made by Health Secretary Jeremy Hunt about the role of GPs in exacerbating problems at overstretched accident and emergency departments.
Earlier this year Mr Hunt said changes to the way GPs provide out-of-hours care have had a ''huge impact'' on accident and emergency services.
"You will remember what happened when politicians made inaccurate and demoralising comments blaming GPs for the pressures on emergency care, and we must be alert to these kinds of attacks on our professionalism and integrity, and fight them with facts," he said.