The number of disabled motorists has fallen by nearly 80,000 in just two years, prompting fresh criticism of Government reforms to disability benefits.
Figures show a 6% fall in disabled people receiving an exemption from vehicle tax since 2015, with 1.267 million people now registered.
While there is no evidence any one cause is behind the drop, the figures support other statistics that show a fall in people being assessed as eligible to claim personal independence payments (PIP).
The latest figures from the Motability charity show 59,000 people have lost their eligibility for a specially adapted vehicle since 2013, as people have switched over to PIP from disability living allowance (DLA).
In total, 230,700 people have been awarded less on PIP than they were on DLA, including 149,200 people between January and October 2016.
The Government said more people receive the highest rate of support under PIP compared to DLA.
Debbie Abrahams, the shadow work and pensions secretary, said: "The Government's flawed PIP assessment process is not fit for purpose.
"It has resulted in thousands of people losing their social security support, with many having their Motability cars removed before their appeals.
"This has forced many disabled drivers off the road and unable to work, or live full and independent lives.
"The anxiety and fear people feel going through these flawed assessments is reprehensible. The whole process is not just counter-productive, it is wrong."
Figures released after a written parliamentary question from Labour MP Peter Dowd show 1,345,446 disabled people received an exemption from vehicle tax as of February 2015, compared to 1,266,523 in February this year.
People can claim the exemption if they receive the higher rate of the mobility component of either PIP or DLA, or specific benefits for injured armed forces veterans.
The DVLA, Department for Transport and the Treasury all said there was no policy they had introduced that would explain the drop off.
Phil Reynolds, senior policy and campaigns adviser at Parkinson's UK and co-chair of the Disability Benefits Consortium, said: "What makes the whole situation worse is that we know people are being put through the unnecessary stress of losing vital support, only to be told they can keep their car when they appeal.
"It's essential that the Government concentrates on fixing this broken system so people with long-term conditions like Parkinson's get the right decision first time, and don't face losing their cars in the first place."
Government figures show that since PIP launched, 178,000 people have had an original decision overturned at mandatory reconsideration or at appeal.
In 2016/17, 65% of PIP decisions that went to appeal were overturned at tribunal in the claimant's favour, according to the latest Ministry of Justice statistics.
SNP MP Kirsty Blackman, the party's deputy leader at Westminster, said: "'These figures show that without question the most vulnerable people in our society are being asked to pay the price of Tory austerity.
"For far too many people, the PIP application process is stressful, worrying and degrading.
"People have to fill out immensely complicated forms about all the things they cannot do and have to go through - often - dehumanising medical appointments.
''After all of this, they are awarded less than they received before. The UK Government's policies are directly making life worse for people."
The Government spends around £50 billion a year supporting people with disabilities and health conditions, more than ever before.
A Government spokeswoman said: "Under PIP 28% of people are now receiving the highest rate of support compared to 15% under DLA, and there are now more people on the Motability scheme than before PIP was introduced.
"PIP looks at the way an individual's health condition or disability impacts them on a daily basis and decisions are made following consideration of all the evidence available."