Patients are facing "creeping charges" for NHS care, a consumer organisation has warned.
The majority of adults pay full price for prescriptions
The issue has been highlighted by the National Consumer Council.
The poor, the elderly and people with long-term health problems are particularly badly hit, it has warned.
It said charges such as those for prescriptions, glasses and dental care were increasing, and new charges were being added.
The current prescription, dental and optical charge arrangements are intended to ensure resources are targeted on providing care for those most in need
Department of Health spokesman
The NCC is calling for investigation into what should be classed as free "core" NHS services.
It wants a Core Services Commission to be set up to look into the issue.
'Punishing the poor'
The NCC says there are inconsistencies throughout the NHS charging system.
In England, 80% of adults under 60 pay prescription charges of £6.30 per item.
The NCC says the list of exempt conditions has not been updated since 1968.
People with mental health problems, or conditions such as asthma, Parkinson's disease, cancer, multiple sclerosis or cystic fibrosis must pay for many of their prescribed medicines and dressings.
More than seven out of 10 people have to pay for NHS dental check-ups and treatment. People must pay 80% of the cost of a course of treatment up to a maximum of £366.
Deirdre Hutton, chairman of the NCC, said: "The system particularly punishes the poor. It deters them from taking up their prescriptions, having eye tests and going to the dentist.
"Creeping charges are probably cock up rather than conspiracy.
"Nevertheless, they spawn unfairness and inconsistencies that compound existing health inequalities."
She added: "Charging people for non-essentials such as hospital access to a TV or the internet is one thing.
"Charging them for services essential to their health is quite another.
"Creeping charges fundamentally undermine the ethos of the NHS - that it will provide essential services free at the point of delivery."
But a spokesman for the Department of Health said: "The current prescription, dental and optical charge arrangements are intended to ensure resources are targeted on providing care for those most in need, and that no-one need be deterred from obtaining any necessary treatment on financial grounds, whilst making the best use of finite public funds."