Around 75,000 people on disability benefits have been underpaid and are owed a significant sum between them, with the whole error estimated to cost around £500m to put right.
Errors have been made in the last six years when paying people Employment and Support Allowance (ESA) who transferred to it from incapacity benefits.
T he Department for Work and Pensions (DWP) confirmed the errors, which affected people applying for ESA between 2011/12 and 2014/15 after a BBC investigation last year.
So far DWP has contacted around 1,000 people so far and has begun making repayments.
Frank Field, chairman of the Commons work and pensions select committee, said the problem was on a scale of “historic proportions”, according to the BBC.
He said: “I’m still gobsmacked at the size and the nature and the extent and the coverage of people that have been wrongly impoverished by the department getting it wrong.”
In addition to the repayments, it will also cost the government to process the repayments.