Employment minister Chris Grayling says he is confident glitches in the system used to decide who is fit to work have been fixed. Two years after the new 'work capability test' was introduced, what's it like for those who go through the assessment?
Katherine Lass often feels self-conscious using her wheelchair in public.
"Often you get people looking at you as if to say, you can't be disabled. You're too young to be disabled," she said.
At 27, Katherine is one of the country's top wheelchair badminton players and a regular at live action role-play festivals, where she and her boyfriend act out scenes from Dungeons and Dragons games.
As she walks around her car and puts together her wheelchair, it's easy to see why some people might do a double-take. At first glance, Katherine looks fit and able.
But with fibromyalgia and ME, she says she is not capable of holding down a job and is one of many thousands of people claiming employment support allowance - a form of benefit paid to those who are medically unfit for work.
"I can do things in short bursts," Katherine told BBC Radio 4.
"But the way the fibromyalgia and ME affect me means that I can't do things repeatedly over a long period.
"Most jobs involve an eight-hour shift and I can't do that. I just get too tired."
In order to qualify for employment support allowance, people like Katherine have to be assessed by the Department of Work and Pensions (DWP).
After filling in a form, most claimants are asked to attend a "work capability assessment".
These are carried out by the private company, Atos, which is paid £100m a year to produce medical reports on claimants' fitness for work. The reports are used by the DWP to help decide who qualifies for benefits.
Atos has been criticised by disability campaigners who say the system they use is too crude to deal fairly with people with complex health problems.
"We're not saying that there shouldn't be a test to ensure that people are genuine claimants," said Dave Skull from the mental health group, Mad Pride.
"But none of this is about actually helping people to get back into work.
"It's really all about cutting the benefits bill. It's a mechanical tick box process."
Employment minister Chris Grayling insists there are no targets and says the system is about transforming lives by helping people back to work.
"What we have in this country is more than two million people on incapacity benefit, many of whom have been on it for years and years and years," he says.
"Effectively the system has said, 'you're on benefits, we'll write you off for the rest of your life'. And I just don't think that's good enough."
Atos won the contract to assess new claimants for employment support allowance under the previous government, which also took the decision to phase out the old incapacity benefit and set a timetable for reassessing incapacity benefit claimants.
Mr Grayling decided to get Atos to reassess those claimants too.
Shortly after her assessment, Katherine received a letter from the DWP telling her that she had been found fit for work. She scored zero points in her assessment. Claimants generally need 15 points or more to qualify for employment support allowance.
"When I got the medical report, I had to check it was my name and National Insurance number on the front," said Katherine.
"It was so inaccurate that I honestly thought they'd sent me someone else's by mistake.
"One of the things that really got to me was from the physical examination.
"It said that all my movements appeared pain free even though I had cried out in pain several times during the assessment."
Katherine appealed against the decision and took her case to a benefits tribunal.
There she was awarded 30 points and so qualified for employment support allowance - though she will have to be reassessed in six months.
Mr Grayling says the system has been improved since Katherine was assessed in January.
A rolling review has been put in place and he has given DWP staff greater freedom to over-rule the advice of Atos assessors.
But the tribunal system is clogged up with appeals against decisions made before the reforms and extra judges have been hired to try to clear the backlog.
The cost of the appeals is thought to be between £50m and £80m.
And even successful claimants say the system needs further fine-tuning.
Vic Shipsey is registered blind and was found unfit for work after being assessed in August - months after the system was improved.
He said: "At 58 and with my eye problems, it's a bit late for me to start looking for new trades.
"If they had only asked my eye surgeon, he could have told them that without me having to go through a medical examination.
"It was a very stressful and worrying time. I had a few sleepless nights. I don't see why it should be so stressful for genuine people."
Mr Grayling says he is "very confident" that the number of decisions being overturned on appeal will fall as a result of improvements to the assessment system.
"I happen to think that the system we inherited from the previous government was flawed," he says.
"It was too impersonal, it didn't do the job properly.
"I'm very confident that with a much more human touch as the whole process goes through, we'll have something where the decisions are more robust."
Can You Touch Your Toes? will be broadcast on Radio 4 at 20:00 GMT on Tuesday, December 20 or You can listen online to it here after it is broadcast.