Jim McKenzie of the Citizens Advice Bureau (CAB) said some people had seen their DLA withdrawn or reduced by a shake-up in the benefits system.
“The system has ground to a halt, it’s struggling because of the number of appeals,” he said.
The government said about 39% of rejections were overturned in England.
‘Ground to a halt’
Mr McKenzie said of DLA applications said: “It’s done on a points basis. It’s raised the barriers higher as to what is being defined as someone not being able to work.”
Sharron Ryan, 41, from Pendeen, was diagnosed with MS in 2010 and said it took her five months to overturn the DLA rejection.
“It was almost like the person who assessed my claim had not even read my claim form,” she said.
“I’d burned myself in the kitchen because my balance was so bad and they said ‘you’ve stated you don’t need help in the kitchen’.
“I can’t go out by myself because of my balance and they’ve stated ‘you don’t need help outside the house’ and it was just the exact opposite of everything I’d put on the claim form.”
She said after appealing against the decision with a presentation of medical evidence she was approved for DLA in December.
In a statement, the Department for Work and Pensions said: “As a person’s condition changes this can affect their eligibility to DLA, but if someone disagrees with a decision they can appeal and their case will be looked at again.”
It added that it was also reforming DLA to “target support at those who need it most” which would see medical evidence presented at an earlier stage.