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.
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.
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.