More than 50,000 disabled people have had specially-adapted vehicles taken away by the Government, a charity has said.
The Motability scheme entitles disabled people to lease a new car, scooter or powered wheelchair using part of their benefit.
But thousands of people are now being denied Motability as they transfer over from disability living allowance (DLA) to the controversial new disability benefit PIP.
The latest figures from the Motability charity show 51,000 people have been taken off the scheme after a reassessment for personal independence payments (PIP) since it launched in 2013 - 45% of all cases.
Of these, more than 3,000 have since rejoined after the decision to refuse them PIP was overturned.
The Department for Work and Pensions (DWP) says a fraction of PIP decisions are overturned, while those taken off the Motability scheme are eligible for £2,000 of support.
But charity Muscular Dystrophy UK said 900 cars are now being taken away every week, as more people are rejected for PIP.
Conservative MP Peter Bone said: "You need it for mobility purposes and maybe you use it for work, but because you lose your PIP award you lose the car at the same time.
"You appeal against the PIP award and ultimately the tribunal awards you back the PIP, but you've already lost the car and maybe your job because of it."
Mr Bone said the Government should let people keep their Motability cars until they have gone through the appeal process.
"The Government could quite easily put that right and it wouldn't cost a significant amount of money at all," he added.
The number of people eligible for Motability funding has halved during the reassessment process since PIP launched in 2013, according to Muscular Dystrophy UK.
It said 126,300 of the 254,200 people who were eligible for Motability funding under DLA and had been reassessed for PIP are now no longer eligible.
DWP figures show that since PIP launched, more than 160,000 people have had their original rejection overturned at mandatory reconsideration or at appeal.
Some 65% of decisions are now overturned at tribunal in the claimant's favour, according to the latest Ministry of Justice statistics.
Nic Bungay, director of campaigns, care and information at Muscular Dystrophy UK, said: "This is having a devastating effect on quality of life.
"Muscular Dystrophy UK is now calling on the DWP to reverse a fiercely contested change in the rules.
To qualify for the higher level of the mobility component of PIP, which is needed to get a Motability vehicle, a person must be unable to walk unaided for 20 metres, compared with the previous distance of 50 metres under DLA.
If an appeal is successful PIP arrears are paid in full to the claimant and they can rejoin the Motability scheme immediately if they repay their transitional support money, or else within six months of the date they left the scheme.
A DWP spokeswoman said: "The reality is that, since PIP was introduced in 2013, more than two million decisions have been made; of these just 7% have been appealed and 3% have been overturned.
"But we constantly review our processes, to make sure they are working in the best way possible."