The man responsible for improving a controversial sickness benefit test has told the BBC he is going to make unannounced visits to job centres.
Professor Malcolm Harrington will do the spot checks to see if changes he has recommended to a test for people claiming Employment and Support Allowance are actually happening.
He told Radio 4's You and Yours that staff should be "nicer to people".
All claimants are being reassessed to see if they are fit to work.
To be eligible to continue receiving the benefit, people have to undergo a medical test called a Work Capability Assessment - introduced by the last Labour government.
The coalition government asked Prof Harrington to review the test after complaints from disabled people, doctors, and charities that people were wrongly being found capable of working and losing benefit money as a result and that 40% of people who appealed had the decision overturned.
Prof Harrington, a former professor of occupational health at the University of Birmingham, concluded there were serious problems with the assessment process and made a series of recommendations to improve it - all of which were accepted by ministers.
The test is carried out by assessors from private firms - but the final decision on their fitness to work and which benefits people should receive as a result is taken by Job Centre staff.
As part of his task of regularly reviewing the process for five years, Prof Harrington said he would be visiting job centres to see how they had implemented the revised procedures.
"I just want to turn up. I just want to go there for an hour, no longer, have a word with the manager, and ask the decision makers: 'Have things changed for you, is it better than it was and if it's not why isn't it?".
The process of assessing eligibility for ESA - which replaced incapacity benefit in 2008 - began across the UK in April. About 11,000 tests are being carried out each month.
Prof Harrington said he acknowledged his recommendations were only beginning to filter through the system and may not yet be fully implemented across the country but he said new claimants should see significant improvements and he would be "astonished" if this was not the case.
"The job centres should be less mechanistic and more human, nicer to people," he said.
"They have changed the telephone system, they've changed the words they use from the call centres, the wording on the letters.
"There is more opportunity to have a dialogue with the claimant, and so the claimant is told early on what it is they can expect to happen."
Employment Minister Chris Grayling recently told a Commons Select Committee that the medical assessment, conducted by healthcare firm Atos, has been "downgraded" in importance.
Prof Harrington said the medical test was not the "be all and end all" but he stressed that claimants had to make sure that all corroborative evidence in their case was made available to be considered.
The changes to the test would give greater authority to Job Centre staff, he added, to make their own decisions rather than just "rubber stamp" the outcome of the medical tests.
"They collect all the information from the claimant, they ask the claimant who is their preferred health care advisor.
"They collect the ATOS assessment, they bring it all together, and … before they make a decision, they contact the claimant and say 'this is what I'm going to do, have you got any other information you want me to consider?'
'That, I think, will be a fairer and more effective assessment and should involve fewer people going to appeal because they feel they've had a decent deal."
The Department for Work and Pensions say they are committed to ensuring the Work Capability Assessment (WCA) is as fair and accurate as possible.
"That is why we will keep it under independent review for five years to ensure it is working properly and have accepted all the suggestions made by Professor Harrington in his first review," it said.
"We are looking forward to receiving his second later in the year. These reforms are vital and will allow us to help those who can work into work and continue to support those who cannot."
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