More than 90 families have launched a challenge against a care assessor to claim back about £1m in care costs, a solicitor has said.
Arden and GEM Commissioning Support Group faces allegations it did not properly assess patients for NHS care and wrongly rejected funding claims.
It works for about 30 clinical commissioning groups (CCGs).
Solicitor Martin Ryan said it was "not fit for purpose" but the group insisted it provided a "professional service".
Mr Ryan, who is dealing with cases involving 25 CCGs, told BBC Inside Out East that in each case people were seeking payment for long-term care provided for loved ones.
He said NHS funded care had been denied to them by Arden and GEM.
"I am categorically stating that Arden and GEM are not fit for purpose, cause delay and totally unnecessary waste of time and resources, incur unnecessary costs to the NHS - and therefore the taxpayer - as well as patients, clients, estates and representatives, and should not be used," he said.
Rosalind Thompson, of Rushden, Northamptonshire, said her late father, Charles Dewis, was denied care from Bedfordshire CCG after the family's claim was assessed by Arden and GEM.
He had senile dementia and died in October 2008 aged 84.
Mr Ryan claims Mr Dewis' family should have received funding for his condition and was wrongly rejected for funding in 2007 and 2008.
"They [Arden and GEM] have under-scored levels of need. They've not followed the process correctly," he said.
Bedfordshire CCG said it was "not able to comment on individual cases".
"Any case that is being taken to the NHS England Independent Review Panel (IRP) will be scrutinised by an independent panel to review the funding decisions made," said a spokesman.
A spokesman for Arden and GEM said: "We aim to provide a professional service at all times and if patients and families believe we have fallen short of our high standards, we would encourage them to complain formally.
"We are aware that Mr Ryan is acting on behalf of a number of families applying for retrospective funding for the care of their relatives but cannot comment on individual cases.
"Arden and GEM has processed nearly 8,000 retrospective claims for families seeking reimbursement.
"So far, around 1,100 retrospective funding decisions have come through the local appeal process run by Arden and GEM and 103 of these applications are now being reassessed."
Last year BBC Inside Out East reported claims by three health workers that medical opinions had been ignored in the assessment of NHS payments to patients receiving care.
These claims were denied by Arden and GEM.
A spokesman for NHS England said: "Spending on continuing healthcare (CHC) is going up as more people are being supported, but within the national rules it's then up to local health services to decide who is eligible for this particular state funding.
"The big differences in spending across the country suggests there is potential to make the process more efficient as the majority of people put through a CHC assessment turn out not to need it."
For more on this story, watch Inside Out East on BBC One at 19:30 GMT on Monday.
- 10 September 2017
- 20 July 2017