Some claimants are waiting more than six months for their cases to be assessed, including those with terminal illnesses.
The Work and Pensions Committee report looked at, among other things, the Personal Independence Payment (PIP) and its effectiveness in assessing disabled people's fitness for work.
Committee chair MP Anne Begg told HR magazine the use of private third-party companies Atos Healthcare and Capita Healthcare to assess claims had exacerbated the problem.
"Why can't this be brought back in-house to the DWP? The Government, along with the public, has lost faith in its third-party providers. They're very hard to replace though. Because of the damage to these companies' brands, the DWP would struggle to find another company willing to take this position on," she said.
The committee suggested that a lack of sufficient planning had led to problems in estimating the time it would take to assess PIP claims.
"The planning period was only one month," she explained. "Even with the best will in the world these claims cannot be completed in a month, so no one had actually tested the system and looked for delays at every stage before going live."
The committee also criticised the DWP's use of language when discussing disabled claimants. Negative rhetoric could undermine people's confidence to get into work if they are declared fit, or to carry on with the assessments if they do not believe they are fit.
Begg said that all the positive language used could be blown out of the water by one negative comment in communications from the department. She said the use of such language could be damaging.
