As many as half a million are either having to find the funds to pay for treatment themselves, or going without, says academic Mark Russell.
The Department of Health has pledged to look into the allegations.
Footcare is vitally important for older people, as foot problems can rob them of whatever mobility and independence they have.
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It's absolutely appalling what's going on in NHS footcare services at the moment
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Mark Russell, researcher
Among elderly diabetics, neglecting footcare can allow the effects of poor circulation to go unchecked - leading to unnecessary suffering, and perhaps even lower limb amputations, which might have been avoided.
However, Mr Russell's own survey suggested that many people who need either chiropody or podiatry are being told that they cannot have it on the NHS.
He told the BBC: "I've never seen a deterioration in standards that we are now witnessing over the past five years.
"It's absolutely appalling what's going on in NHS footcare services at the moment. It's happening in nine out of 10 health authorities."
Training programme
Ann Stevens, from the Society of Chiropodists and Podiatrists, said: "I think elderly people are really suffering foot pain, foot discomfort, which really impacts on someone's ability to remain an independent member of society.
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The NHS has no intention whatsoever of withdrawing from those services
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John Hutton, Health Minister
"People who do not get appropriate treatment may be at far higher risk of full hospitaliation or dependence on other services."
However, Health Minister John Hutton told the BBC: "The NHS has no intention whatsoever of withdrawing from those services.
"There is clearly seriously a problem there and I want to make some enquiries.
"But we continue to provide services to more than two million patients a year and those figures have remained broadly static."
He said that training courses for podiatrists and chiropodists would see a large increase in staff in those areas.
He said that the new "national service frameworks" for both the elderly and people with diabetes would emphasise proper footcare.
He said: "The figures that we collect, on which my information is based, do not show that half a million people have lost their podiatry and chiropody service."
Shadow health spokesman John Baron said: "It is appalling that some of the most vulnerable people in our society are being denied the vital chiropody and podiatry treatment that they need and deserve."
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