A third of the young people who claimed Disability Living Allowance in childhood failed to qualify for the adult version of the benefit, Personal Independence Payment
Disability charity Scope said the number of young people losing disability benefits at 16 was unacceptable and said the PIP assessment process was fundamentally flawed and in need of an overhaul.
Around 328 young claimants in the area - 55% - saw their benefit award rates increase or stay the same after moving to PIP but 193 had their awards withdrawn, according to data from the Department of Work and Pensions.
Of the cases disallowed between October 2013 and October last year, 145 applicants were rejected after failing to score enough points - awarded to reflect their mobility and care needs - during the assessment part of the process.
There were also 15 youngsters who were refused due to failing to attend assessments without good reason and 33 who did not meet the basic eligibility criteria.
Another 64 applicants were approved for PIP but had their award rate cut.
Where the number of outcomes is nil or very low, figures have been excluded so totals could be higher.
A spokesman for the Department of Work and Pensions said over 60% of child DLA claimants go on to receive PIP, with award rates staying the same or increasing for over half of all claimants.
He said the Government was working hard to ensure disabled young adults received support, adding: “PIP is designed to assess how people are affected by their disability, rather than just the disability itself.
“Many DLA claimants have not undergone any kind of assessment of their needs for several years and as a result their condition or their needs arising from their condition may have changed substantially.”
DLA and PIP are awarded to help individuals and families meet the extra costs associated with long term health conditions and disabilities, with claimants currently entitled to receive up to £152 a week tax free.
Ken Butler from Disability Rights UK said sudden withdrawal of benefit support at a young age could be traumatic and impact upon household finances, care payments, local authority support entitlement and the ability to remain in education.
He said: “If a young person is still meeting the conditions for DLA while a teenager, it is difficult to see why they would not continue to have the same level of needs at 16.
“The level of support and extra financial costs do not disappear overnight when a disabled young person becomes 16.”
James Taylor from Scope said: “The Government must ensure that disabled young people don’t lose out on vital income to cover extra costs at such a crucial time in their lives.”