More than 200,000 original decisions on Personal Independence Payment (PIP) have been changed since April 2015, according to analysis of Government figures.
Those unhappy with a PIP decision must first go through a mandatory reconsideration, in which the Department for Work and Pensions reviews the decision.
Following that, a claimant can appeal to an independent tribunal if they are still unhappy with their award.
DWP and Ministry of Justice figures released this week show that overall, since April 2015 104,198 people have won their PIP appeal at independent tribunal, and a further 100,600 have had their original decisions changed at mandatory reconsideration.
This includes 91,597 people in 2016/17, over which time DWP made just short of a million initial decisions on PIP claims and reassessments.
This means that the equivalent of almost one in 10 original decisions made by DWP on PIP claims last year was overturned.
The most recent figures show a growing proportion of people taking their PIP claim to appeal are having their case upheld.
Between July and September 68% of 21,019 appeals went in the claimant's favour, the highest quarterly figure since records began in 2014.
The figures for Employment and Support Allowance (ESA), a long-term sickness benefit which uses the same mandatory reconsideration and appeal process, tell a similar story.
Over the most recent year for which figures are available, 68% of 70,173 ESA claims taken to appeal were overturned in the claimant's favour.
Mark Atkinson, chief executive at disability charity Scope, said: "Decisions not to award PIP are being overturned at their highest ever rate, and the number of successful appeals over ESA has surged.
"Disabled people tell us this financial support is a lifeline, enabling them to live independently, visit friends and family and be part of their community.
"It's imperative that assessments for PIP and ESA are overhauled to iron out the mistrust, lack of transparency and routine inaccuracies which disabled people report on a weekly basis."
It comes as DWP announced it was going to drop a performance indicator that 80% of mandatory reconsiderations for both PIP and ESA should uphold the original decision.
Campaigners had branded the 80% figure a target, with welfare minister Sarah Newton acknowledging the figure had caused "anxiety and confusion" in a letter to the Work and Pensions select committee.
Analysis of DWP data shows that in the first seven months of 2017/18, 17.8% of new PIP claims and 22.3% of reassessment decisions taken to mandatory reconsideration by the claimant ended up with the award being changed, a significantly lower rate compared with cases taken to appeal.
Labour MP Frank Field, chairman of the Work and Pensions select committee, said: "It is great news that the target has been dropped and we congratulate the department on this response.
"This is a great victory for the thousands of PIP and ESA claimants who have responded to our inquiry, and for anyone going through this process, who can now go to the first stage of appealing a benefits decision with more confidence that the reconsideration will be fair and impartial."
DWP is in the process of recruiting, training and deploying around 150 presenting officers to present its case at PIP and ESA tribunals.
The average salary in a DWP presenting officer's most common pay grade is £25,631, according to figures released to Parliament.
In August the Independent reported that £39 million was spent in 2016 by DWP to stop sick and disabled people claiming benefits, which also included figures for ESA.
Last month Sir Ernest Ryder, senior president of tribunals, said the quality of evidence provided by the DWP in benefits cases was so poor it would be "wholly inadmissible" in any other court.
A DWP spokeswoman said: "More than 2.6 million PIP decisions have been made, and of these only 8% have been appealed and 4% have been overturned.
"The majority of successful appeals are overturned because people have submitted more written or oral evidence.
"The latest official research shows that 76% of PIP claimants are satisfied with their overall experience and we continuously review our processes to ensure they're working in the best way possible."
Copyright (c) Press Association Ltd. 2017, All Rights Reserved. Picture (c) John Stillwell / PA Wire.