More than 220,000 people have been given "zero scores" in both parts of the test for disability benefits in only 18 months, according to new figures.
Labour's Angela Eagle called the statistics "deeply worrying" and said it reflected growing numbers of cases causing people great distress in her constituency.
Personal Independence Payment (PIP) assessments score people points based on their ability to carry out different tasks.
For each component of PIP, people need at least eight points to get the standard rate or 12 points to get the higher enhanced payments.
Figures obtained by Ms Eagle through written parliamentary questions show 220,390 people scored "zero points" in the tests for both the mobility and daily living component of PIP between April 2016 and October 2017.
Analysis by the Press Association also suggests a greater proportion of claimants are now scoring zero on both parts of the test.
The Department for Work and Pensions (DWP) said decisions on PIP were made after careful consideration and more people were now receiving higher rates.
However, former welfare minister Ms Eagle said: "It is deeply worrying to see just how many people are being written off and given scores of zero for their PIP assessments.
"This reflects recent experience in my constituency, where increasing numbers of people are contacting me in great distress after receiving scores of zero.
"This includes people that have received PIP in the past, and have actually seen a deterioration in their health since then."
Overall, 347,210 cases have scored zero on either or both parts of the PIP test since April 2016.
The figures obtained by Ms Eagle show that 15,320 people scored zero points on both parts of the test in October, the highest monthly figure over the previous year.
Between April and October the equivalent of little more than one in six tests scored zero on both parts, the lowest ratio since PIP launched in 2013.
Previous figures released to Parliament showed that in 2016, 13,130 people had a decision on PIP overturned having previously been scored zero.
More than 180,000 people who previously claimed Disability Living Allowance (DLA) have been denied PIP as they have transferred between the two systems.
"Under the Tory Government's assessment process tens of thousands of people with chronic disabilities have had their payments removed, and many with mobility problems have had their vehicles taken from them," said Ms Eagle.
"These figures show just how punitive the assessment process is, with vast numbers of people each year receiving scores of zero and not even coming close to receiving PIP.
"It is clear that the current system is failing people in real need and is not fit for purpose."
A DWP spokeswoman said: "We introduced PIP to replace the outdated DLA system.
"PIP is a better benefit which takes a much wider look at the way an individual's health condition or disability impacts them on a daily basis, and is tailored to suit each individual's needs.
"Under PIP, 29% of claimants receive the highest rate of support, compared to 15% under DLA.
"Decisions for PIP are made after careful consideration of all the evidence provided by the claimant, including supporting evidence from their GP or medical specialist, and anyone who is unhappy with a decision can appeal."