The MS Society said nearly half (48 per cent) of those questioned who had an assessment for employment support allowance (ESA) felt it was of harm to their health.
And more than a third (36 per cent) of those who had a face-to-face assessment for personal independence payment (PIP) felt the same.
The charity said the current disability benefits assessments do not accurately take into account the fluctuating and hidden symptoms of MS and the impact this has on sufferers.
It has launched a new campaign “MS: Enough: Make welfare make sense”, and is also calling for the system to take adequate account of evidence provided by experienced professionals who understand the person’s condition.
Of the 1,800 respondents who completed the survey, nearly a third (32 per cent) also said benefit changes have led them to cut down on food; more than a quarter (28 per cent) have cut down on transport; and two out of five (41 per cent) are socialising with family and friends less.
Nearly one in 10 (9 per cent) said they have reduced spending on attending hospital appointments while 9 per cent have cut down on medical treatment or prescriptions as a result of benefit changes.
PIP, which replaced disability living allowance (DLA), has been described as unfit for purpose after it was beset by backlogs and delays which left many disabled people waiting in excess of six months, and in some cases more than a year, for their claim to be processed.
The work capability assessment system that determines if someone will receive ESA has also been dogged by controversy, with heavy criticism of the tests used to decide whether applicants are eligible.
The charity wants the government to undertake a full impact assessment of any further changes they undertake to disability benefits, including the knock-on effects on other areas of public spending such as health and social care.
Michelle Mitchell, chief executive of the MS Society, said living with a chronic, disabling neurological condition such as MS can be expensive.
“Having MS is enough; it should not be made harder by a welfare system that doesn’t make sense for people living with the condition,” she said.
“Lack of understanding of the condition and the failure to use information from medical professionals is causing stress or contributing to relapses and deteriorating health.
“This is counter-intuitive to a system designed to support people with disabilities.”