Many families are having to wait longer than a year for final decisions on who should pay for their relatives' care, NHS England has said.
Those who have been refused free care under the continuing healthcare (CHC) programme can ultimately appeal to the authority.
However, the average wait for appeals to be heard has risen in one year from 304 days to 444 days, it said.
Claimant advocates said the "alarming" rise was "prolonging family stress".
NHS England has been approached for comment.
Continuing healthcare is fully funded by the NHS for some people with "long-term complex health needs".
Jane Wallington, from Gosport, Hampshire, first applied for free care for her mother Beryl in 2013 and was still awaiting a final appeal hearing.
She said she was forced to sell her late mother's home to pay nursing home fees of nearly £80,000.
Ms Wallington said: "It's seven years down the line and still we're waiting. It's been the most frustrating experience of my entire life.
"It's all just lost in the mechanisms of the NHS. I'm shocked to the core that they treat people like this."
NHS England, responding to a BBC Freedom of Information request, said the length of the wait for final appeals had risen by 46% in the year to January.
It said 2,024 cases were waiting to be heard by an Independent Review Panel.
Lisa Morgan, from Hugh James solicitors, said the increase was "extremely alarming".
She said: "The delays are unacceptable and they cause emotional and financial strain on families, when they may have to be making unnecessary decisions about selling homes."
Ms Morgan said she blamed late or poor-quality paperwork from local NHS Clinical Commissioning Groups (CCGs) rather than NHS England.
Beacon, a not-for-profit organisation which represents CHC claimants, said "processes and quality vary hugely" at the CCG stage.
Managing director Dan Harbour said the "worrying" increase in the waiting time "prolongs the stress and uncertainty for families".
NHS Clinical Commissioners, which represents CCGs, said the groups were "working hard to improve their systems and processes".
The body said CCGs faced an increasing workload due to an ageing population.
West Hampshire CCG, which initially refused Ms Wallington's application for free care, said her case was caught in a "regional backlog of CHC independent reviews".
Chief operating officer Mike Fulford said: "We understand the additional upset that this causes at an already difficult time for families of loved ones, such as Ms Wallington, and we apologise for the delay."