The Department for Work and Pensions (DWP) has spent more than £100m in just over two years on administering reviews and appeals against disability benefits, figures show.
Tens of millions of pounds a year are also spent by the Ministry of Justice on the appeals, about two-thirds of which were won by claimants in the past 12 months.
The costs were described as “staggering” and a former Conservative minister said “something is seriously wrong with the system”.
The DWP said a small proportion of decisions were overturned and most employment and support allowance and personal independence payment claimants were happy with their assessments.
But the department is facing questions from the work and pensions select committee over the figures, following claims that it was not given similar information for MPs’ inquiry into PIP and ESA.
Figures obtained through a freedom of information request show the DWP has spent £108.1m on direct staffing costs for ESA and PIP appeals since October 2015.
The amount covers mandatory reconsiderations, an internal DWP review and appeals to tribunals run by HM Courts and the Tribunals Service.
Neil Heslop, the chief executive of the disability charity Leonard Cheshire, said: “To spend this amount on admin fighting to uphold flawed decisions that shouldn’t have been made in the first place is staggering.
“Thousands of disabled individuals have had to fight to receive support to which they are legally entitled.”
Since October 2015, 87,500 PIP claimants had their decision changed at mandatory reconsideration, while 91,587 others won their appeals at tribunal.
In the first half of 2017-18, 66% of 42,741 PIP appeals went in the claimant’s favour.
The figures for ESA since October 2015 show 47,000 people had decisions revised at mandatory reconsideration and 82,219 appeals went in the claimant’s favour.
So far in 2017-18, 68% of 35,452 ESA appeals have gone in favour of the claimant.
Ros Altmann, a Conservative peer and former DWP minister, said the money could be spent on benefits for those who need them, rather than the costs of fighting claims.
“Disability benefits need an overhaul and, of course, we must not let people make bogus claims, but the extent of the appeals we are seeing clearly indicates that something is seriously wrong with the system,” she said.
Figures released to the select committee inquiry show further costs to taxpayers.
The Ministry of Justice spent £103.1m on social security and child support tribunals in 2016-17, up from £92.6m the year before.
In a letter to the committee, the then justice minister Dominic Raab said the average cost of an appeal had more than doubled to £579 in 2014-15 because PIP cases “now comprise a much larger proportion of the caseload” and require more members on the tribunal.
The MPs are due to publish the results of their inquiry on Wednesday.
Frank Field, the committee chairman, has written to Esther McVey, the work and pensions secretary, to ask why MPs were not given the information.
The DWP gave the committee the average cost of a mandatory reconsideration and appeal for PIP and ESA, but Field said it was unable to work out the full cost because information on whether PIP appeals were from new claimants or those being reassessed, which have different costs, was not available.
“That this data was provided in response to an FoI request, but not for our report, is doubly regrettable, since the key theme of our report is the need to introduce much greater trust and transparency into the PIP and ESA systems,” Field wrote.
A DWP spokeswoman said it was working to improve the process, including recruiting about 190 officers who will attend PIP and ESA appeals to provide feedback on decisions.
“We’ve already commissioned five independent reviews of the work capability assessment, implementing more than 100 of their recommendations, and two independent reviews of PIP assessments,” she said.
“Meanwhile, we continue to spend more than £50bn a year on supporting people with disabilities and health conditions.”