Controversial changes to the way disability payments are made were introduced in some regions of the country on Monday, ahead of a national roll out.
Personal Independence Payments (PIP) will replace the Disability Living Allowance (DLA) for new claimants in Merseyside, Cumbria, Cheshire and the North East, amid claims from charity Scope the "flawed" reforms could see more than 600,000 disabled people lose their allowance.
New claimants signing up to PIP will be "based on an assessment of individual need", according to the Department for Work and Pensions (DWP).
The new assessments will focus on an individual's ability to carry out a range of key activities necessary to everyday life, and will include face-to-face meetings with assessors and regular reviews.
The government says the current system is too complex and has not been reformed since its introduction in 1992. PIP will be rolled out across the UK for new claimants from June, and for existing claimants from 2015.
The motivation for the reforms comes from DWP figures that show more than 70% of claimants get DLA for life, and a belief that changes in individual circumstances mean there should be more regular assessment.
But Richard Hawkes, chief executive of Scope, said: "DLA needs reforming and could be better targeted to meet the extra cost people face. But disabled people are frightened by the government's plans. They believe it's just an excuse to cut their support.
"For months now we have been saying the government's assessment for PIP is deeply flawed. It doesn't take into account all the barriers disabled people face in daily life."
Esther McVey, minister for disabled people, said: "Disability Living Allowance is an outdated benefit introduced over 20 years ago and needs reform to better reflect today's understanding of disability.
"At the moment, the vast majority of claimants get the benefit for life without any systematic reassessments and around 50% of decisions are made on the basis of the claim form alone - without any additional corroborating medical evidence.
"The PIP will include a new face-to-face assessment and regular reviews - something missing in the current system. This will ensure the billions we spend give more targeted support to those who need it most."