Millions of people claim disability benefit in the UK
Disability campaigners say thousands of people who are unable to work are being wrongly denied incapacity benefit.
Charities including the Disability Alliance, Mind and Citizens Advice say the government's system of assessing claimants is not working.
They say people face hardship while appealing to restore benefits, and that many more are incapable of appealing.
The government says it is developing a new assessment system that will cut the number of wrong decisions.
Just over 2.6m people claim incapacity benefit - a figure the government wants to cut by about a million before 2015.
Out of these, 100,000 people fail the Personal Capacity Assessment (PCA) each year and, from that figure, 25,000 people a year successfully appeal against a decision to deny them incapacity benefit.
While they appeal, their benefit is cut by as much as £30 a week.
Citizens Advice say that other benefits, such as Disability Living Allowance, can be cut after a failed PCA, so some claimants are missing out on even more than that.
The Minister for Disabled People, Anne McGuire, told BBC Radio 5 Live that some of the problems were already being addressed.
She said: "We recognise that the overturn rate at appeal is higher than we would want and often this is because people present more evidence at the appeal than perhaps they have previously presented.
"But we're looking at our new medical assessment and new work capability assessment, which is coming in October and which will, I think, be a bit more sensitive to some of the issues, particularly for those who have a mental health condition."
Paul Treloar, from the Disability Alliance, said the current system was not working.
"People report to us that the examinations can often feel rushed, they don't feel like they're being properly listened to.
"And we have had numerous examples where the medical reports contain statements that don't actually reflect the person's home circumstances."
Len Wheeler, who had his incapacity benefit cut after a medical assessment before it was restored on appeal, also said he was assessed too quickly.
"You had to give a straightforward answer, you couldn't talk too much, he'd just stop you," he said.
Speaking to BBC Radio 5 Live, Mr Russell also described the unpredictable nature of his condition.
He said: "This depression, it changes. I can be alright one day, and then totally depressed the following day.
"I personally would be better off in work, for the way my mind is. Boredom sets in, then I realise I'm not fit enough for work at times."
The Department for Work and Pensions says it is developing a new medical assessment which will be much better at identifying the needs of people with mental health problems, and should reduce the number of wrong decisions.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.