Around 16,000 disabled people could lose their cars and scooters when benefit changes take effect, according to campaigners.
About 80,000 people will lose their mobility allowance when disability living allowance (DLA) is replaced by personal independence payments (PIP) next month, campaigners told Holyrood's Welfare Reform Committee.
Some 46,200 get cars and scooters under DLA but a third stand to lose them under PIP, Inclusion Scotland chief executive officer Bill Scott said.
UK Welfare Reform Minister Lord Freud's claim that cutting the walking distance at which people are deemed mobile from 50m to 20m would not see a cut in recipients was called into question.
People could disqualify themselves if they make it to the benefits assessment centre, convener Michael McMahon suggested.
The changes could leave people stuck in their houses for the rest of their lives, according to campaigners.
But Conservative MSP Alex Johnstone, the only member of the committee from a UK coalition party, accused an SNP MSP of spouting conspiracy theories and took issue with a campaigner referring to the new housing benefit under-occupancy penalty as a "bedroom tax".
Mr Scott said: "Around 80,000 will lose entitlement to the DLA when the new enhanced PIP is brought in.
"For those on the higher rate, it's not just the substantial loss of income that's the worry, it's the means of accessing wider society that will be put to question, because if they lose the higher rate they will also lose automatic entitlement to the blue badge, which can assist people in parking in city centres.
"They could also lose automatic entitlement to concessionary travel, and because the high rate is also the passport to motability vehicles, we have used Disability Rights UK and other sources to work out that about one in three claimants use the higher rate DLA to lease a motability vehicle, so about 16,000 people could also lose their vehicles."