Nearly a third of people living with multiple sclerosis (MS) have had their initial claim for disability benefits rejected after the system was reformed, campaigners have warned.
Data obtained by the MS Society suggests 31% of new claims for personal independence payment (PIP) by people with MS were "disallowed" by the Department for Work and Pensions.
Some 4,100 people had their application rejected between April 2013 and April 2017, according to the figures obtained through a Freedom of Information request.
A further 1,100 claimants with MS qualified for PIP but were then rejected in a reassessment, despite MS being a long-term, progressive condition.
DWP said more people with MS received higher levels of support under PIP than the old system, while assessments looked at how claimants were affected over the majority of days in the year.
Michelle Mitchell, chief executive of the MS Society, said: "It's insulting that so many people who are diagnosed with a long-term, incurable condition are being told they don't qualify for support.
"These latest figures show PIP isn't just hurting those who've been moved across from the old system, but also new people who are trying to get support for the first time.
"PIP is meant to help manage the extra costs of living with a disability and assist people to be more independent.
"But it's a tougher system than disability living allowance (DLA), with much stricter rules.
"In too many cases, assessments fail to reflect the barriers people with MS face."
The MS Society is now calling for an overall review of PIP.
It wants to see better training for assessors, an evaluation of how PIP takes hidden symptoms like pain and fatigue into account, and improvements around providing medical evidence.
Earlier this year, the charity said at least £6 million a year had been taken from people with MS who have been reassessed from DLA.
This month DWP made changes to PIP criteria it said would boost payouts to some 10,000 people.
But Ms Mitchell (pictured) said: "Rather than tinkering around the edges, the Government needs to review the whole system to make sure it works more effectively for those it's designed to support.
"Having MS is hard enough.
"It shouldn't be made harder by a welfare system that doesn't make sense."
It comes as Frank Field, chairman of the Work and Pensions Select Committee, said the committee's inquiry into PIP and Employment and Support Allowance had been "deluged" with more than 3,000 letters.
A DWP spokeswoman said: "PIP assessments look at how individuals are affected by conditions such as multiple sclerosis over the majority of days in a year, rather than just assessing ability on a single day.
"Under PIP, 36% more people with multiple sclerosis receive the highest rate of support than under the previous DLA system.
"More than 2.6 million PIP decisions have been made, and of these 8% have been appealed and 4% have been overturned.
"In the majority of successful appeals, decisions are overturned because people have submitted more evidence."
More than 61% of those with MS who have moved to PIP from DLA are receiving the top rates, while DWP says degenerative conditions like MS are monitored through regular reassessments.
PIP was brought in to replace DLA in April 2013.
In 2016/17, 65% of the 70,329 PIP decisions that went to appeal were overturned in the claimant's favour.
Separate figures from the Motability charity show 67,000 people had cars on the scheme taken away as they transferred from DLA to PIP, 45% of all cases.
Of these 4,500 rejoined the Motability scheme after the decision was overturned.
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