Disability charities have added their voices to concerns about the Welfare Reform Bill, published today by Prime Minister David Cameron.
The National Autistic Society (NAS) and Leonard Cheshire Disability (LCD) have raised concerns about the move from Disability Living Allowance (DLA) to Personal Independence Payment (PIP) which is one of the measures included in the Bill.
NAS expressed the fear that the change would result in those with hidden disabilities like autism missing out on vital benefits.
Mark Lever, the charity's chief executive, said: "We have substantial concerns about the introduction of a face-to-face assessment for the new benefit.
"Autism is a complex condition and it's much harder to assess the impact of the disability on daily living than for other disabilities. This has already proved to be hugely problematic with the work capability assessment for Employment Support Allowance (ESA), resulting in costly appeals and unnecessary distress for an already socially isolated and vulnerable group.
"Many adults with autism are extremely worried about the possibility of losing benefits they desperately rely on and the proposed reforms to the welfare system are pushing them to a state of near constant anxiety.
"With 30% of people with disabilities already living below the poverty line, it is understandable that there is such great concern.
"We therefore urge the Government to ensure that the design of the new assessment specifically covers the needs of people with autism if they are serious about their promise to help those who need it most."
Guy Parckar, acting director of policy and campaigns at LCD, said: "The Bill proposes replacing DLA with the new PIP. With this change comes a drastic reduction of spending - in the future the Government plans to spend £1 billion less each year on DLA...
"We need assurances that reforms to this benefit will not push even more disabled people below the poverty line."
Mr Parckar also addressed the changes of payments to people in residential care. He said: "The proposal to stop DLA mobility component for people in residential care is still included in the Bill. However, it is positive news that the Government has agreed to formally review this proposal.
"Disability charities and disabled people have overwhelmingly told the Government that this is a change that will have a devastating impact on people's lives and runs completely counter to all the Government's stated objectives to support disabled people to live independently.
"As this Bill moves through Parliament we will be urging the Government to listen to the evidence from disabled people and not press ahead with this change...
"But it is imperative that these reforms challenge levels of disability poverty, rather than leave disabled people more isolated and facing further financial hardship.
"Disabled people are twice as likely as non-disabled people to live in poverty in the UK."
Mr Cameron said the reforms were "tough, radical... but fair".
He insisted that while encouraging people - including those with disabilities - to seek employment, the new system would also guarantee support for those who were genuinely unable to work.
He said: "Those who can, should; but, of course, those who can't, we always help.
"I passionately believe that the welfare system should be there to support the needy and most vulnerable in our society and provide security and dignity for those in old age.
"That's why the system was born, that's what it's always done - and with me, that's the way it will always stay.
"But that doesn't mean the welfare system shouldn't change. It has to change - because it just isn't working."
NAS is a charity for people with autism (including Asperger syndrome) and their families, LCD aims to change attitudes to disability and provides services to support disabled people.
For more information go to http://www.autism.org.uk and http://www.lcdisability.org.