DLA changes: Tanni Grey-Thompson and Iain Duncan Smith
18 January 2012 Last updated at 15:06 GMT
The crossbench peer and former Paralympian Baroness Grey-Thompson questioned the work and pensions secretary over changes to the Disability Living Allowance.
She said some people were "terrified" about the proposals, and claimed up to 500,000 people could lose out.
Iain Duncan Smith said the reform was intended to offer a "sustainable" allowance that would go to the right people, with some losers and some gainers.