From October, all 2.6 million people currently on incapacity benefits will have to be assessed for ESA eligibility, leading some people to argue the current rejection rate will be passing people as fit to work, when they are not.
Already, the ESA system has become the most appealed benefit in the UK - with 8,000 people appealing against the decision the government comes to each month. So far, 40% of these decisions are overturned and ruled back in favour of the claimant.
Speaking on Radio 4, the designer of the ESA back-to-work programme, Professor Paul Gregg, admitted there were shortcomings: "We are hearing a lot of anecdotal and factual evidence in terms of what is happening to claimants to say that we have got a serious problem here," he said, " We need to rectify it before it starts being applied to the large stock.''
The Work Capability Assessment, which measures people's capability to work has been in place for a year. In that time only 5% of ESA claimants have scored enough points to be deemed unable to work, and receive benefits of up to £108.55 per week.
A further 11% of ESA claimants were eligible for the "work related activity group" at a weekly rate of £89.80 per week. Claimants receive tailored help and attend compulsory work-focused interviews. Under the previous medical test, up to 83% of incapacity benefit claimants were found unfit for work.
The Department of Work and Pensions said: "People need much more support to manage their conditions and get help to find work, and moving them to ESA is the best way to do that."
Government is passing the sick as fit to work
On the day the Government is setting out plans to get more people off disability benefits, an investigation by the BBC has found two-thirds of people so far applying for the new Employment Support Allowance (ESA), have been rejected because their disability is not deemed as preventing them from working.