Around 700,000 requests for formal care and support made by older people in the last 12 months were unsuccessful, research shows.
This is equivalent to half of all requests, according to Age UK.
In 23% of cases the older person was found by their council not to meet the eligibility criteria set for the social care system and that was the end of it.
In 46% of cases the older person was found ineligible but their council then referred them onto other services in the hope that they could assist.
The charity said the figures show how difficult it is to qualify for care within the UK’s “shrunken social care system”.
Between 2010/11 and 2018/19, total spending on adult social care fell by £86m in real terms, representing a 4% reduction in local authority spending.
Although spending has now largely recovered from its lowest point in 2014/15, the older and disabled population has significantly increased, meaning social care spending per head of the adult population has fallen by 6% per person over the same time period.
The analysis suggests 1.5 million over-65s in England are going without all the help they need to carry out at least one essential “activity of daily living”.
Meanwhile, more than a fifth of all the calls to Age UK’s information and advice line concern social care.
Caroline Abrahams, Age UK’s charity director, warned that if people are forced to go without care it is a recipe for emerging health problems to turn into crises, possibly leading to a hospital stay and an irreversible decline in health.
“Faced with too much demand and too little supply, our social care system is effectively under siege,” she said. “Councils do their best with the resources they have but there are simply not enough to go round. One result is this vast number of older people whose applications for help are rejected and another the long waits for an assessment to have your case looked into at all.”