The retreat of the health service is stealthy and haphazard, as a creeping postcode lottery of cuts gradually erodes the “national” in NHS. IVF, hip and knee operations are being cut back randomly in some regions. In some places patients can only get one cataract fixed: seeing with one eye is enough.

Waiting lists for hospital care just topped 4 million people, waiting times lengthening as A&E admissions rise means fewer planned operations, with extreme variations by hospital. The NHS is ordered to cut an impossible £22bn by 2020 – but there is no national instruction as to what. Politically, it’s easier to leave local decision-makers to take the blame.

Little by little services vanish. Prof Azeem Majeed, head of primary care and public health at Imperial College and a Lambeth GP, has just blown the whistle in the British Medical Journal on the latest withdrawal of a service: many clinical commissioning groups (CCGs), including his own, are banning GPs from prescribing anything that can be bought over the counter. Bristol, Lincolnshire, Dudley, Telford and Essex are among many others issuing the same edict.

At first glance it makes sense not to prescribe what most people can get for themselves, until you consider poorer patients who can’t afford the 22 drugs now banned for prescribing. Majeed says “Low-income families often can’t afford ibuprofen, or gluten-free products for coeliac disease sufferers. A single mother on low pay with two children can’t afford the £10 it would cost for nit treatment.”

Pain relief will be denied for those suffering headache, backache, toothache, migraine, fever or those needing antihistamines for hayfever, treatments for thrush or eye infections. With food banks handing out over a million emergency food kits and Unicef reporting that 10% of UK children suffer “severe food insecurity”, basic but essential over-the-counter medicines are beyond the budgets of households who struggle to provide meals.

It is, say the CCGs, a waste of doctors’ time to be handing out easily available treatments. Majeed agrees, but points out that there was a special system for the poor: the minor ailment scheme. It allowed patients already entitled to free prescriptions to access certain free over-the-counter treatments on the NHS from a pharmacist without seeing a GP. This year these are being cut back in his own area and many others. Minor ailments don’t feel “minor” to those in great pain.

The ban on all over-the-counter medicines comes with a screed of cant about the importance of promoting 'self-care'

NHS England estimates £400m can be saved by these cuts, though it is left to local CCGs to impose, randomly. But Majeed doubts that saving. Instead he points to where the NHS really could save large sums on prescribing by negotiating a better price for generic drugs from monopoly suppliers. “The NHS is very bad at tackling this.” He gives the example of Tamoxifen, a breast cancer treatment, which he says, cost just 10p a tablet in 2011 but rose to £1.21 last year.

Britain’s extreme poverty and inequality needs to be taken into account by the NHS: health inequalities are growing in sickness and early death rates. Few will dispute a new ban on GPs prescribing malaria medicines and some travel vaccines: those who can afford long-distance travel can afford these. But the ban on all over-the-counter medicines comes with a screed of cant about the importance of promoting “self-care”.

The British Medical Association says local CCGs have no right to impose this limit, as it breaches GPs’ contracts. Majeed says of course prescribing needs to be constantly reviewed, “But that should be done nationally, not just ad hoc. If each CCG has its own list of drugs there will be postcode prescribing.”

Equal access was the founding idea of the NHS, written into the NHS constitution. Until now, every health secretary has tried to iron out local variation. But abandoning the “national” in the NHS was the intention of Andrew Lansley’s 2012 Health and Social Care Act, a deliberate fragmentation by tendering and intense competition, encouraging private providers and devolving priorities to the whim of local commissioners.

While the government still tries to deny NHS cuts, despite a real decline in per capita funding by next year, it’s much easier politically to avoid ever announcing what services will be withdrawn, but to leave it to hapless CCGs locally. Recently I reported on the vanishing podiatry service, forcing most people to go private – and causing 135 avoidable diabetic amputations a week. Everywhere you look, around the margins of the NHS, services are shrinking back. Now the poorest are being denied basic pain relief and other treatments that most regard as absolutely essential treatments in everyday life.

• Polly Toynbee is a Guardian columnist