Patients in some parts of England are not getting care they need, while in others they are being overtreated because of practices that risk damaging people’s health and wasting money, admits the NHS.

Too many people are being diagnosed late with cancer while at the same time GPs are too frequently prescribing antibiotics unnecessarily, it says on Friday in a new report.

Similarly, too few of those who have had a stroke are being admitted within four hours to a specialist hospital unit, which is recognised as being crucial to their survival and recovery.

And while some of the fast-growing number of diabetics receive most of the eight annual checks on their health that all are supposed to get, some only undergo four.

The findings are contained in the latest edition of the NHS Atlas of Variation in Healthcare, which highlights a series of wide disparities in how patients are treated depending on where they live.

“This atlas exposes some inconvenient truths about the extent of clinical practice variation in care for some common conditions”, said Sir Bruce Keogh, NHS England’s national medical director.

John Newton, chief knowledge officer at Public Health England (PHE), said the document – an in-depth analysis of NHS performance across England – showed that “while some patients are missing out on the right care, others are being given care they don’t need.”

For example, while clinical guidelines state that fewer than 10% of patients should be prescribed antibiotics by GPs, in some parts of the country as many as 16.8% receive them, though in others it is just 6.8%.

In some places as many as 60.8% of patients found to have cancer were diagnosed early, when the disease was still at stage one or two. But in others it is as low as 22.7%, which may mean they need more invasive treatment or risk significantly reducing their chances of survival.

Julia Verne, head of clinical epidemiology at PHE, said England’s 211 GP-led clinical commissioning groups had to do more to ensure that more cancers were diagnosed early, perhaps by persuading a greater number of people to be screened.

With strokes, 40% of patients are not admitted quickly to a specialist unit, even though National Institute for Health and Care Excellence guidelines make clear that all should. “The Atlas clearly shows more stroke patients need to be admitted to specialist stroke units more quickly,” said Verne.

There is also a pronounced “postcode lottery” – a 2.7-fold variation in areas – in the likelihood of a GP offering patients who may have dementia an “enhanced service” for diagnosis and support.

While medical care can vary in its quality, safety and the outcomes achieved, those are examples of what NHS chiefs called “unwarranted variation” – practices which undermine patients’ health or waste NHS resources.

Experts behind the atlas said that addressing these disparities in clinical practice could help the NHS make the £22bn of efficiency savings it has pledged to realise by 2020.