Disabled people are "losing out" on jobs because of a government support scheme that is "no longer fit for purpose", campaigners say.
Access to Work - which gives workplace support to disabled people - is beset by errors, with many having support cut, charity Inclusion London said.
One deaf, leading artistic director said having her funds capped would mean she could no longer work full time.
The government said it was "committed to supporting disabled people" in work.
'It gave me confidence'
Access to Work is a government programme aimed at helping disabled people and those with physical and mental health conditions that make it difficult to work.
By providing grants - such as to help people with learning disabilities understand written information, or transport for those with physical impairments to attend meetings - it aims to enable people to find or stay in employment.
According to government figures, £103.9m was spent on the scheme in 2016-17, helping about 25,000 people across England, Scotland and Wales.
Jenny Sealey, chief executive at Graeae Theatre and co-artistic director of the London Paralympics opening ceremony, told the BBC's Victoria Derbyshire programme she had relied on the support - which enabled her to pay for sign language interpreters - to get to the top of her field.
"Because I've had Access to Work I've become professional, I've learnt my trade, I've learnt how to cope in big meetings," she said.
"It gave me the confidence to say, 'I want to be co-artistic director at the Paralympics opening ceremony'."
'Terrified' of the future
A 2004 government review suggested for every £1 of money spent on Access to Work, £1.48 was generated for the Treasury.
But since 2015, new claimants have had the money they can receive each year capped at 1.5 times the average salary - around £41,000.
From April 2018, this will affect existing claimants too.
The report estimates 90% of those affected by the cap will be deaf people.
Ms Sealey said having her support capped will mean no longer being able to work full time.
"[At] the thought of having to cut my hours, I can feel me - Jenny - shrinking, becoming this small person, feeling quite terrified of what my future is.
"I can't believe this is going to happen, it makes me feel quite sick."
The government says by capping the amount a claimant can receive, the scheme can reach as many people as possible.
Ellen Clifford, the author of a new report into the scheme for Inclusion London, said the scheme had enabled disabled people to "not only get jobs, but to have a choice of jobs - to go into the same range of professions as non-disabled people".
One sign language interpreter said it had allowed deaf and disabled people to "smash the glass ceiling".
But Ms Clifford said in recent years that they needed to reduce the amount of support they were getting.
"There was a noticeable increase in hostile attitudes from advisers - accusations that people were a burden on the taxpayer."
Ms Clifford said there was also a "disproportionate impact on deaf customers", with call centres "ill-equipped to deal with non-hearing customers".
She added that the level of administrative errors being made was "making the scheme unworkable for people".
One deaf woman who spoke to the programme, Geraldine O'Halloran, said her budget had been cut twice in 2017 because of administrative errors.
A spokeswoman from the Department for Work and Pensions said it was "committed to supporting disabled people to get into employment or keep their jobs.
"Last year 25,000 people had their request approved by Access to Work, an increase of 8% from 2015-16."
Watch the Victoria Derbyshire programme on weekdays between 09:00 and 11:00 on BBC Two and the BBC News Channel.