Demands for efficiency savings on the cost of care for some sick and disabled patients could put patient safety at risk, MPs have said.
Officials want local health bodies to cut the amount spent on the NHS's Continuing Healthcare funding packages and NHS-funded nursing care by hundreds of millions of pounds over coming years.
But the Public Accounts Committee said it is "not clear" how this can be done without increasing the threshold for eligibility or by limiting the packages available.
"Both of which will ultimately put patient safety at risk," the influential committee said in its latest report.
NHS Continuing Healthcare (CHC) is a package of care provided outside hospitals, such as in people's homes or in a care home, that is arranged and funded solely by the NHS through clinical commissioning groups (CCGs).
People must have a significant health need that goes above and beyond usual social care needs, such as help with washing or dressing.
The Public Account's Committee's new report on CHC states that "too often" patients' care is compromised because they are not made aware of the funding available or are not guided through the "hugely complicated" process of accessing funding.
Last year the National Audit Office described how decisions on whether somebody is eligible for continuing healthcare should be made within 28 days, but one in 10 people waits longer than 100 days.
The committee also found that people were waiting "too long" to learn whether they were eligible for funding, adding: "In some cases people have died whilst waiting for a decision.
The MPs added that there is "unacceptable variation" in accessibility of the service across the country, which could be caused by CCGs interpreting the assessment data "inconsistently".
The report adds: "NHS England wants CCGs to make £855 million of efficiency savings in CHC and NHS-funded nursing care spending by 2020-21, but it is not clear how they can do this without either increasing the threshold of those assessed as eligible, or by limiting the care packages available, both of which will ultimately put patient safety at risk."
Meg Hillier (pictured), chairwoman of the committee, said: "Conditions such as Alzheimer's disease and multiple sclerosis have devastating effects on sufferers and their loved ones. Help with meeting the costs of ongoing care can make a critical difference to their quality of life.
"It is therefore distressing to see the system intended to support such people fall short on so many fronts.
"Oversight of CHC funding has been poor and NHS England's demand that clinical commissioning groups make big efficiency savings will only add to the financial pressures on the front line."
The report calls on NHS England to provide a breakdown of how the proposed efficiency savings will be achieved, with assurances these savings will not lead to restricted access to care for patients, among other recommendations.
An NHS England spokesman said: "We disagree with the committee's opinion on this, not least as CHC spending is set to increase not fall. What's more, the big differences in spending between local areas suggests the NHS is right to continue to push for efficiencies here."
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