Thousands of people in Wales could be wrongly paying for their long-term health care, it is claimed.
Experts said the rules over long-term nursing care were unlawful
Experts in care law have told BBC Wales that the criteria used to decide who has free NHS care are unlawful.
A survey by the programme Week In Week Out found most questioned thought the current funding system was unfair.
The Welsh Assembly Government said it planned training for decision-makers and an improved appeals system with a role for community health councils.
While the Scottish Parliament has introduced free personal care on top of free nursing, there is no similar scheme in Wales.
The BBC investigation found that private residential and nursing homes can amount to £20,000 a year for those who are refused free long-term NHS care.
Catherine McDougall, from Penarth, has been diagnosed with Alzheimer's Disease, and her family said she was a risk to herself and others.
Her son, Iain, said he was shocked when his mother, a former nurse who often cared for elderly people, was denied free NHS care.
He said: "My mum took care of elderly people in exactly the state that she is in now. She would be absolutely furious, she would be wanting to rip someone's head off, quite frankly.
'Hour of need'
"I'm talking about all people of that generation. They have been conned.
"They were told, at the early conception of this National Health Service, that if they contributed to it for their working life, they would be taken care of in their hour of need and that is not happening."
Luke Clements, a solicitor and lecturer in community care law at Cardiff Law School, said that he believed the guidelines and criteria used to judge whether someone is entitled to free care are unlawful.
He said: "I think it's an enormous con job. The law hasn't changed since 1946. Parliament hasn't changed anything.
"No minister has stood up and said 'we don't do this any more', so as a lawyer, I would say this is a con job. I think it's an outrage.
"I think the reason we are not seeing a huge outcry is that this is happening to people at a very difficult time in their lives."
The BBC Wales survey, carried out by Beaufort Research, found that of those with experience of elderly care, more than half thought the way elderly care is funded was either extremely or very unfair. But 7% thought it was very or extremely fair.
Of those who say that people who could afford it should contribute towards their care, 70% said the value of a person's home should not be taken into account when assessing affordability.
Welsh Health Minister Brian Gibbons told the programme that the policy of making personal care free at the point of need had proved more expensive in Scotland than planned.
Week In Week Out is screened at 2235 on BBC1 Wales