Tens of thousands of "excess deaths" could be linked to cuts to health and social care budgets, according to new research.
A study by academics said an "unprecedented" rise in the number of deaths in England and Wales in 2015 could have been due to the "relentless cuts".
There were 30,000 extra deaths in 2015, the greatest rise in mortality for almost 50 years in England and Wales, articles published in the Journal of the Royal Society of Medicine said.
Researchers from the London School of Hygiene and Tropical Medicine, University of Oxford and Blackburn with Darwen Borough Council said without "urgent intervention" the increases in mortality could continue.
To explain the huge increase in the number of deaths, the academics looked at four possible causes.
The potential reasons they explored were; possible problems with the data, whether there had been an "environmental shock" such as a natural disaster or war, whether there was a major epidemic or whether there had been "widespread failure of the health and social care system".
After ruling out data errors, cold weather and flu as main causes for the spike in deaths, the researchers concluded that "the evidence points to a major failure of the health system, possibly exacerbated by failings in social care".
The researchers said that in 2015 NHS performance "worsened markedly".
Areas of the NHS that the report says worsened in January 2015
- Ambulance call out times being below target.
- No rise in A&E attendances but waiting times increased.
- Waiting times for diagnostic tests and consultant-led care increased.
- The number of operations cancelled for non-clinical reasons rose.
- Delayed transfers for care peaked, leading to a shortage of beds.
- Staff absence rates rose and more posts remained empty as staff had not been appointed.
The researchers say the findings should be seen "in the context of the worsening financial situation of the NHS".
The impact of the budget cuts on the NHS since the 2010 elections has been "profound" says the report.
The researchers said the amount spent on the NHS has failed to keep pace with the demand and this has been exacerbated by "dramatic reductions in the welfare budget of £16.7 billion and further reductions in social care spending".
They added: "With an ageing population, the NHS is ever more dependent on a well-functioning social care system.
"Yet, social care has also faced severe cuts, with a 17% decrease in spending for older people since 2009, whilst the number of people aged 85 years and over has increased by almost 9%."
The authors concluded: "The possibility that the cuts to health and social care are implicated in almost 30,000 excess deaths is one that needs further exploration.
Co-author Professor Danny Dorling, from the University of Oxford, added: "It may sound obvious that more elderly people will have died earlier as a result of government cut backs, but to date the number of deaths has not been estimated and the government have not admitted responsibility."
A spokesman for the Department of Health in England said the report was biased and excess deaths reported each year varied "significantly".
"Every year there is significant variation in reported excess deaths, and in the year following this study they fell by nearly 20,000, undermining any link between pressure on the NHS and the number of deaths.
"Moreover, to blame an increase in a single year on 'cuts' to the NHS budget is arithmetically impossible given that the budget rose by almost £15 billion between 2009-10 and 2014-15", the spokesman said.
A Welsh Government spokeswoman said it was "unhelpful" to consider the Welsh and English systems together as "there have been no cuts to health and social services in Wales".
She added: "We have protected both health and social services spending, because we recognise the importance of taking an integrated approach to delivering them.
"We have ensured that health spending per head has been higher in Wales than in England for the last five years.
"We will have invested over half a billion pounds worth of additional funding for the Welsh NHS in the first two years of this new Government; an extra £169 for each Welsh resident. Spending on health and social services per head in Wales is 6% higher than in England.
"Mortality rates are prone to fluctuation and caused by many different factors in society, not just health or social care, so any view of a single cause should be treated with caution."