Hospitals in England and Wales are refusing referrals for obesity operations on costs grounds, a snapshot survey of doctors suggests.
Demand for obesity operations is rising
GP magazine Pulse polled 20 consultants in charge of such surgery and found half bounced referrals back to GPs.
It means the severely obese - at risk of conditions like heart disease - have to rely on lifestyle changes and drugs.
Obesity experts said it could cause deaths. The Department of Health said funding was decided at a local level.
Hospitals are funded by NHS bodies called primary care trusts in England or local health boards in Wales.
Only the most severely overweight patients are referred for gastric banding and gastric bypass operations to reduce the size of the stomach.
Under NHS guidelines, this includes those with a BMI - a measurement which uses height and weight to determine obesity - of over 40.
Ideal weight is classed as between 18.5 and 25 BMI.
In the past five years, there has been a 650% rise in referrals for obesity surgery in some areas, Pulse said.
Some 12 of the 20 consultants quizzed said their units were struggling to cope with the rise in numbers, with half sending patients back to GPs.
Dr David Haslam, clinical director of the National Obesity Forum, said the behaviour was "outrageous".
"It's a completely false economy. To limit on the grounds of cost is disgraceful.
"People will be dropping down dead because of it."
Professor John Baxter, president of the British Obesity Surgery Society, added: "To say there's underfunding is a massive understatement. It's appalling. There should be a public inquiry in my view."
But David Stout, director of the NHS Confederation's PCT Network, said: "I would be surprised if trusts are blocking this on financial grounds.
"It is more likely that the referrals are inappropriate. Obesity surgery should be a last resort."