A Sheffield professor has criticised the failure to provide 43-a-day drugs to breast cancer patients in some parts of the country.
Thousands of women with breast cancer are being denied the cheap drugs, to try to stop cancer returning, according to a new report.
The study for Breast Cancer Now also claims progress on tackling breast cancer is also stalling in other ways, with declining rates of women turning up for mammograms and longer waiting times for treatment.
The charity says there is still inadequate action on the number of women given cheap drugs to stop their cancer coming back - and has accused the NHS of a 'dereliction of duty'.
Research shows that when post-menopausal women are given bisphosphonates within six months of initial diagnosis, the risk of breast cancer spreading to their bones within 10 years falls by nearly a third - 28 per cent - and there is an 18 per cent reduced risk of death.
Figures suggest the drugs could prevent more than 1,000 deaths a year from breast cancer - one in 10 of all breast cancer deaths - and potentially help 35,700 women diagnosed with the disease each year.
Prescribing bisphosphonates could also save the NHS £5 million each year across the UK, the new report said.
Breast Cancer Now used Freedom of Information laws to ask Clinical Commissioning Groups in England if they routinely funded bisphosphonates.
Only a fifth did so - 42 out of 208 CCGs -, while a further six per cent said they had agreed to fund them and were currently implementing the decision.
The picture was better in Scotland and Wales, with two out of three cancer networks offering them.
Baroness Delyth Morgan, chief executive of Breast Cancer Now, said: "In bisphosphonates, we have a simple and cost-effective chance to cut 10 per cent of all UK breast cancer deaths, using drugs already at the NHS' disposal.
"That this is not being taken is nothing short of a dereliction of duty.
"We now call on NHS England to take immediate action to ensure all CCGs are able to prescribe bisphosphonates to all eligible patients."
Rob Coleman, professor of medical oncology at the University of Sheffield, said: "That over 1,000 women a year are being allowed to die unnecessarily from breast cancer is a shameful irresponsibility - particularly when the solution is a safe and inexpensive treatment that within five years would not only save lives but save the NHS precious funds to invest elsewhere.
"The inability of NHS England to action this treatment across the country is totally unacceptable."
An NHS England spokeswoman said: "As well as upgrading modern radiotherapy equipment and ensuring faster access to the most promising new cancer drugs, the NHS is investing £200 million over the next two years in faster diagnosis and modern treatment."
A Department of Health spokesman added: "We have made huge progress on tackling cancer - an estimated 7,000 more people are surviving cancer after successful NHS treatment compared to three years ago and NHS England is leading crucial work to save a further 30,000 lives a year by 2020.
"Any decision to prescribe treatments is a matter for clinicians and should be based on a patient's need and the best available evidence."