An MP said the figures, released in Parliament, “make a mockery” of the controversial tests on people to determine whether they should receive the payments.
Caroline Lucas said constituents with “debilitative illnesses and mental health issues” had contacted her fearing they would lose their benefits as a result of the test – called a work capability assessment.
Employment Minister Chris Grayling confirmed that in Brighton and Hove, 56 per cent of appeals had been successful in the most recent time-period available – far higher than the national average of 38 per cent.
The tests, by French company Atos Healthcare, have been condemned by disability campaigners for being impersonal and ignoring conditions such as mental illnesses.
As well as new applicants, people already receiving Employment Support Allowance, which used to be called incapacity benefit were also being tested. They face being stripped of the benefit if they are found to be fit to work.
Almost 33,000 people in Sussex will be affected.
The figures showed that almost a third of those applying in Brighton and Hove were rejected.
In the two years up to November 2010, the most recent period available, this meant a total of 1,920 people were found to be capable of work and not eligible for the benefit. Of the 740 people who appealed against the verdict, 420 saw it overturned.
Ms Lucas said: “The fact that more than half of the people in Brighton and Hove who were initially turned down for Employment Support Allowance on the basis of Atos assessments were successful in appealing those decisions makes a mockery of the whole system.
“A number of my constituents have expressed real anxiety about the controversial Work Capability Assessment and are concerned that those suffering from long-term debilitative illnesses and mental health issues are most at risk from losing the welfare support they desperately need.”
Giuseppina Salamone, welfare rights adviser at Brighton and Hove TUC Unemployed Workers Centre, said: “The system has been created so that users who can do small things are believed to be able to work.“The law itself is very tough in addition to this test.”
A Department for Work and Pensions spokesman said: “We are committed to continuously improving the Work Capability Assessment through a series of independent reviews led by Professor Malcolm Harrington and we have accepted all of the recommendations from his first review.
“We expect that Professor Harrington’s recommendations will make the WCA a fairer and more effective assessment, and will ultimately result in a decrease in the number of decisions going to appeal.”