Claimants of the government's disability benefits programme have an "inherent distrust" of the system, an independent review has found.
The second review of Personal Independence Payments said 65% of those who appealed against rejected claims saw the decision overturned by judges.
This, along with a lack of transparency in the assessment process, is damaging trust in PIP, says the report.
The Department for Work and Pensions said it would consider the findings.
Personal Independence Payments or PIP is a benefit for those who need help with extra costs associated with long-term illness or disability.
It was brought in to replace the Disability Living Allowance (DLA) in 2013 and pays claimants up to £139.75 per week, depending on their needs.
The review was carried out by Social Security Advisory Committee chairman Paul Gray, who made a number of recommendations to the government in his first review in 2014.
In his latest report, he said progress against those recommendations had been "mixed", with their implementation either "incomplete or slower" than he had hoped.
Mr Gray is now calling for further measures to increase the transparency of the system for claimants, such as more information about gathering evidence for their claims and voice recordings of face to face assessments.
'High levels' of dispute
He also wants more consistency between the assessors who deal with each claimant.
"A key conclusion of the review is that public trust in the fairness and consistency of PIP decisions is not currently being achieved, with high levels of disputed award decisions, many of them overturned at appeal," said Mr Gray.
"My findings point to the need to build very considerably on current action to improve the way PIP is administered, continuing the direction of travel proposed in the first review."
His report also said that as the programme continues to progress, there should be further evaluations, with results made public to help build trust in the system.
The minister for disabled people, Penny Mordaunt, said: "I'm grateful to Paul Gray for undertaking his second review of Personal Independence Payments.
"His independent work is an important part of making sure our processes are working in the best way possible and we will respond to the recommendations in due course."
'Lack of trust'
Citizens Advice chief executive Gillian Guy said PIP was the biggest issue people sought advice for through her organisation, with almost 400,000 queries in the past year.
"While some parts of the system have got better - such as a reduction in waiting times - we are concerned there is still a way to go in terms of improving the quality and accuracy of the PIP application and assessment process," she said.
James Taylor, the head of policy at disability charity Scope, added: "Today's report reveals that disabled people have a lack of trust in the application process for Personal Independence Payment.
"We want to see the Government overhaul how the assessment process works for disabled people."