The NHS is gambling with patients' health by increasingly banning operations for hernias, cataracts and arthritic joints to save money, one of the UK's most senior medical figures said .

John Black, the president of the Royal College of Surgeons of England, accused NHS primary care trusts (PCTs) of pursuing a "dangerous" course by refusing treatment to patients, who will then suffer unnecessary pain and have less chance of recovering fully.

The NHS in England needs to save £20bn by 2014-15 as part of an efficiency drive. Black said increasing numbers of trusts are postponing or axing provision of dozens of elective surgical procedures, including those for gallstones and tonsil and adenoid problems.

His intervention came ahead of the government's publication of its flagship health and social care bill on Wednesday – the radical shakeup of the NHS which will hand to GPs the power to commission services, and which has been criticised by health bosses and medical leaders.

In a speech , David Cameron will attempt to fight a growing backlash against the NHS's biggest reforms since 1948 by announcing that 141 groups of GP practices in the UK, caring for half of the population of England, have signed up to a "pathfinder" pilot scheme.

The NHS Confederation – backed by the British Medical Association and the royal medical colleges – issued a strong warning that healthcare would suffer as a result of the reforms.

Separately, in a letter to the Times the heads of six health unions, including the British Medical Association and the Royal College of Nursing, warned of their "extreme concerns" about plans to create greater commercial competition between the NHS and private companies within the health service. The speed and scale of the reforms proposed by Andrew Lansley, the health secretary, risks undermining the care of patients by putting cost before quality, they said.

Black told the Guardian he was seriously concerned that "the immediate need to save money by going for the soft targets of elective surgery would leave a lot of people with unpleasant symptoms and build up future health problems. Medically that makes no sense."

He called for an open, honest debate about what the NHS could and could not afford to do, given its financial constraints.

"More and more NHS trusts are introducing more and more of this sort of backdoor rationing by imposing longer and longer waiting times for surgery on patients, or indeed stopping doing certain procedures altogether. This is a dangerous path for the NHS to be adopting, because of the long-term health problems that will inevitably be built up if operations designed to prevent long-term harm are delayed or stopped," said Black.

"By reducing elective surgery you can immediately save money, but at the cost of pain, reduced quality of life and deterioration of health.

"If the NHS continues to save money in this way, we will pay later in terms of future suffering of patients."

Those denied a new hip or knee to replace one affected by arthritis would have reduced mobility and less independence, for example. "Tens of thousands of patients every year are turned from cripples into rehabilitated humans on the NHS thanks to them getting a joint replacement at the right time. To restrict access will result in a lot more people having a lot more pain," he added. "Patients that aren't operated on won't see their symptoms go away; they won't magically get better. Their hip or knee will just degenerate." Delay means an eventual operation is less likely to succeed, he said.

Similarly, men refused a hernia operation could end up developing a strangulated hernia, which requires emergency surgery; and if tonsils are left infected, infection can spread to the middle ear or brain, Black added. Untreated gallstones can lead to complications that can reduce life expectancy.

It is unfair of PCTs to decide to leave patients untreated when their condition would until now have been routinely fixed with surgery, Black said. "Increasing restrictions on cataract removals are a complete disaster. With a cataract, you can't see properly. If there's an operation to restore people's sight to normal, most people would consider that to be mainline NHS work that is routinely provided."

Black criticised PCTs for drawing up lists of procedures they deemed to be of little or no clinical value. Although cosmetic procedures to remove blemishes were unnecessary, it was "odd" that hip and knee replacements had been placed in the same category. Evidence showed that new joints were the second most effective health intervention, after giving up smoking, he said.

The NHS in north-east Manchester has just decided to stop providing 57 types of surgery, at least until April. These include new hips and knees, cataracts, hysterectomies to cure heavy menstrual bleeding, "trigger finger", tonsil removals and all aesthetic procedures, such as tattoo removals. Even surgeries with an 80% success rate have been classified as having "no clinical value".

National NHS bosses made clear that care of patients should not be affected in the quest to save the £20bn. "We have been very clear that NHS organisations should not interpret efficiency savings as budget and service cuts. Every penny saved from efficiency savings – including a 45% reduction in management costs – needs to be invested back in to patient care," said Professor Sir Bruce Keogh, the NHS's medical director.

"Providing the best possible care for patients is our priority."

"Decisions on the appropriate treatments should be made by clinicians in the local NHS in line with National Institute of Health and Clinical Excellence guidance. We would not recommend creating definitive lists of ineffective or inefficient procedures without a clear consensus from clinicians who are experts in the field," he added.NHS leaders hope to agree with specialist groups of doctors and surgeons which effective operations the NHS should fund and which ineffective ones should be withdrawn, Keogh added. "This provides the opportunity to direct taxpayers' money towards effective rather than ineffective treatments."

The Patients Association helpline has received calls from patients whose planned operations had been cancelled without a new date. "Why are patients having to suffer in order to balance the books?" said Katherine Murphy, its chief executive. "I would say to the NHS, think again and think hard, don't make patients the victims of budget cuts and save the money elsewhere."