Minister for Disabled People, Esther McVey, has told Daybreak that the changes will focus benefits on those who need them most.
She said: "Disability Living Allowance (DLA) came out in the 1990s and it was very much about physical disabilities.
"Now we're adjusting it to take into account disability how we understand it today - mental disabilities as well as fluctuating ones.
"So it is actually understanding disabilities more and it is really focusing benefits to where it's needed most."
More top news
The Suitsy: Man creates business suit onesie
Alex Salmond has announced his intention to end a 24-year career at the forefront of Scottish politics. Here is a brief look at his career.
Britain is among the least devolved countries in the world, figures from the RSA show.