Nearly a third of older people with care needs do not receive crucial help, according to an Age UK study.
Without the help of care workers, family, friends or neighbours 31.1% of 65 to 89-year-olds find they have to struggle alone.
Pensioners may struggle with a range of tasks such as taking their medication, eating on their own, getting washed or getting in to the bath, getting dressed, going to the toilet or just getting out of bed on their own.
The Age UK study on ageing shows that 870, 000 older people between 65 and 89 now have unmet social care needs.
It was noted that the number of over 65-year-olds who were using social care services had dropped by 27.2% - from 1,231,000 to 896,000 - between 2005/6 and 2012/13.
This happened even though this age group has grew by more than one million over the same period and there was a rising demand for this kind of support while the amount being spent on social care services for older people has fallen, Age UK argue.
A public consultation on a Care Act 2014, which means local authorities will have to follow new rules determining who is eligible for care, has begun. The Care Act is due to come into force in 2015.
Age UK's charity director Caroline Abrahams described the Care Act as "fundamentally good legislation" but claimed that underfunding means increasing numbers of older people are being shut out of the care system.
She said: "It beggars belief that one in three older people who need some basic help with daily living are now having to do without it. And it is important to remember that the figures we analysed for this research only go up to age 89. It makes you wonder how many more thousands of people in their nineties are being left to struggle alone."
"When older people begin to need some help with essential daily tasks like eating and washing they should expect that it will be there for them, yet it is increasingly beyond their reach. This is profoundly shocking, and it's a direct result of our care system being scaled back at the same time as the population of older people is growing.
"Our national failure to invest properly in social care not only deprives older people of vital support, it also makes no economic sense: for example, an older person who struggles to eat is more likely to become ill and need expensive hospital treatment than if they receive some regular help with their meals: social care helps older people to stay well and keep their independence for longer."
Age UK is calling on the Government to change its eligibility guidance so that every older person who needs some help with an essential daily task can get it.
Ms Abrahams said: "The Government's draft guidance on eligibility for care suggests that from now on, the inability to do just one of these essential things like washing or dressing will not be enough to qualify you for support. It is not even certain that people with dementia who need help to continue to live at home with dignity will be entitled to it.
"Older people deserve so much better."
A Department of Health spokesman said: "We have given an extra £1.1bn to councils to help protect social care services this year - that's on top of additional funding in recent years.
"Councils are ultimately responsible for deciding how to spend their budgets but we agree that we all need to work differently to respond to the challenge of our growing ageing population.
"The Care Act and the Better Care Fund will focus resources on helping people to live independently, which can save money and prevent people from needing more support."
Shadow health secretary Andy Burnham said: " This research paints a depressing picture of a generation of older people facing loneliness, neglect and struggling to cope at home.
"More and more frail and vulnerable people are ending up in hospital."
Mr Burnham said more than 100,000 extra "frail and frightened" people were being taken to hospital via blue-light ambulance.
He added: "David Cameron has allowed home care support to be withdrawn from thousands of people. This is a false economy and one of the main causes of the intense pressure on A&E. Older people who go into hospital are at risk of becoming trapped there.
"The ever-increasing hospitalisation of older people is no answer to the ageing society.
"Labour believes the time has come to bring social care into the NHS so that we can create a service for the whole person, supporting people where they want to be and ending the scandal of older people neglected in their own homes."