The minister for disabled people, Esther McVey, said changes to the benefit system are about "understanding disability in the 21st century" and adapting a system which will work better in the future.
Speaking about the Personal Independence Payment plans, Mrs McVey said: "What we've got to do is ensure the billions of pounds that we spend, really are focused on those people who need it the most."
She added that independent assessments would be carried out along the way, to make sure the Government is "getting it right."
Today's benefit changes are about as sensitive as they come - which is why a cool head is needed to analyse the proposals
The Disability Living Allowance (DLA) will be replaced by Personal Independence Payment (PIP) for people aged 16 to 64 from 8 April.