There are fresh calls for the Government's "increasingly problematic" assessments for disability benefits to be scrapped, after new statistics showed further problems with the system.
Record numbers are now successfully appealing against Government decisions to refuse personal independence payments (PIP) and employment and support allowance (ESA).
The latest figures show around 60% of those that took their case to independent tribunals had the decision reversed in their favour.
The assessment process for both benefits has been a longstanding source of controversy.
The Department for Work and Pensions (DWP) insists that overall a very small percentage of claims get overturned.
But Vicky McDermott, chief executive of disability charity Papworth Trust, said she was not surprised by the increasing success rates.
She told the Press Association: "This reflects the fact disabled people have not had a good experience with assessments in the current format and further action has been required in order for the system to support their needs.
"The system needs to change to avoid disabled people being forced to take action against DWP and taxpayers' money being wasted on appeals and tribunals."
Disability groups have long argued the current system is designed to discourage people from claiming, saving the Government money on the welfare bill.
The Government is set to spend £22 million on hiring 180 new presenting officers to be present at tribunals to fight these cases for the DWP.
The new posts, announced in this year's Budget, come in response to the long-term trend of an increasingly large percentage of cases going against the Government.
The new staff are expected to be in post come the spring.
Claimants looking to appeal against the DWP's decision first have to go through a "mandatory reconsideration" review with the DWP before they can appeal to a tribunal.
The figures for reversals here are far lower, with little more than 10% of claims being overturned.
"Only a small proportion of all ESA and PIP decisions are overturned at appeal - just 3% of PIP and 5.5.% of ESA," said a DWP spokeswoman.
"In the majority of successful appeals, decisions are overturned because claimants have submitted more oral or written evidence."
Ms McDermott, though, called the PIP assessments "increasingly problematic", with many only being classified for two years and subsequently requiring a reassessment.
"This is unsettling for the claimant and wasting Government money," she added.
"We are also concerned that the assessment focuses far too heavily on the physical needs and competencies.
"The tests fail to recognise hidden disabilities, which are often the reasons why disabled people are in need of social security support."
These figures come amid claims from disability groups of further "below the radar" cuts, after a steep fall in the proportion of disabled people being found eligible for out-of-work disability benefits.
The proportion of disabled people applying for ESA who were placed in the support group - for those with the highest barriers to work - plunged by 42% in just three months.
During the same period, the proportion of applicants found "fit for work" - and therefore ineligible for ESA - rose from around a third to nearly half of those assessed.
Disabled researcher and campaigner Catherine Hale told the Disability News Service she feared the Government was "continuing its austerity agenda via the back door", having been forced into a climbdown over cuts to the PIP benefit.
Ms McDermott added: "Papworth Trust believes immediate changes can be made to prevent this alarming rise in appeals and the decline in ESA support group numbers from continuing."
The DWP acknowledges that more people are now being found fit to work, and says this might be partly behind the increase in appeals, given this designation is more likely to prompt claimants to appeal.
A spokeswoman added: "The decision on whether someone is well enough to work is taken following a thorough independent assessment and after consideration of all the supporting evidence from the claimant's GP or medical specialist.
"A claimant who disagrees with the outcome of their assessment can ask for the decision to be reviewed."
She also said the proportion of people being found fit to work remained below 2013 levels.
PIP is extra money awarded to help people with everyday life if they have an illness, disability or mental health condition.
ESA has replaced incapacity benefit and claimants are split into three groups: those fit to work, who are not eligible to claim ESA; the support group, who are deemed not well enough to attend work or interviews; and the work-related activity group, who the DWP believes can return to work with the right support.