More than one in two people with illness or disabilities who took the government to court after losing out on benefits went on to win their case, data shows.
Analysis of Freedom of Information responses shows more than half a million people were wrongly denied disability benefits from 2013 to 2018.
Charities and advice providers said the figures show the government’s benefits tests were beset by poor decision-making and obvious inaccuracies.
Most of the appeals concerned Employment Support Allowance (ESA), which is paid to people who cannot work because of illness or disability; the Disability Living Allowance (DLA), which is paid to people with extra care or mobility needs; and Personal Independence Payments (PIP), which was introduced to replace DLA.
Daphne Hall, the vice chair of the National Association of Welfare Rights Advisers, said: "The reason for the high success rates [at tribunals]...is because of the poor assessments carried out by health professionals.
"The DWP tend to base their decision purely on these assessments and disregard other evidence sent in by the claimant."
Initial assessments are carried out on behalf of the Department for Work and Pensions (DWP) by the private companies Capita and the Independent Assessment Services (formerly called Atos), which have come under criticism for scoring claimants too harshly.
Figures for the North West:
The success rate for disability, sickness and incapacity benefits appeals at tribunal has risen from 37% to 69% over the five-year period
Overall, some 142,838 people who had lost disability, sickness and incapacity benefits appealed against their decision at tribunal, with 70,455 succeeding
When all types of benefits are considered, the success rate rose from 32% in 2013-14 to 66% in the period from April 2018-December 2018 with some 78,399 people successful over the period
Between 2013-14 and 2014-15, there was a 78% drop in the number of appeals against all types of benefits which were decided
Since 2014-15, the number of benefits appeals cleared at hearing has risen year on year
In 2017, Britain’s most senior tribunal judge, Sir Ernest Ryder, senior president of tribunals, also said the quality of evidence provided by the DWP was so poor it would be "wholly inadmissible" in any other court.
Capita and Maximus said the majority of people were satisfied with the process, and they were working with charities and disabled people's organisations to improve their services further.
The government says appeals represent a small percentage of all benefits claim it handles.
Do you have a story for us? Want to tell us about something going on in Tameside, Oldham or Rochdale? Let us know by emailing email@example.com , calling us on 0161 621 6515 , tweeting us @rev962 or messaging us through our Facebook page. All contact will be treated in confidence.